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JUNE 1972 AUSTRALIA'S LARGEST-SELLING ELECTRONICS & HI-FI MAGAZINE 


Fiji and New Guinea 60c 
Malaysia $2.50 
New Zealand 60c 














meet Sony’s 



ECM-22P 


ECM-16 


(and 

little) 


in truly sensitive sound recording 


Here is Sony’s front line in a brilliant range of electret condenser microphones. They offer superior quality, great utility and 
pleasure to all kinds of operators — private and professional in the hi-fidelity field. Despite their comparatively low prices, 
their sensitivity and the quality of their sound equals the best condenser units available anywhere, as well as possessing 
additional advantages such as extremely low power requirements, stability, and easy miniaturisation. 


Here are details of the four illustrated: 


r 




The Sony MX-12 



One of a range of four microphone mixers, the 
superbly designed MX-12 is a low impedance, three 
channel stereo or six channel monophonic micro¬ 
phone and/or line input mixer with independent 
head type level controls for each channel. It is 
equipped with phone plug inputs too, and costs 
about $149. e 

V _ J 


ECM-22P 

A professional quality microphone with “phantom” power feed 
system so that Lt can be used in studios of broadcasting stations. 
It has a wide range of frequency response with sharp directivity. 
About $158. 

ECM-21 

A brilliant performer unidirectional microphone highly suitable for 
hi-fi recording or broadcasting and adaptable for hand or stand 
use. About $61. 

ECM-19B 

An excellent unidirectional microphone with built in wind screen. 
Ideally suited for outdoor use or interview work. About $36. 

ECM-16 

A tiny omnidirectional high quality microphone ideal for incon¬ 
spicuous placement. Can be hung around the neck or clipped on a 



JACOBY 


SYDNEY: 26 2651, MELBOURNE: 
329 6866. ADELAIDE: 93 2388/9. 
BRISBANE: 44 4488, PERTH: 28 5725, 
yy % f LAUNCESTON: 2 5322, Agents: 

KEMPTrlORNE CANBERRA: 479010 . Newcastle: 

*■* " 61 4991, WOLLONGONG: 711132. 


For further information please fill in the Reader Information Service coupon in this issue 










ABC certified circulation in excess of 48,000 


Readership in Sydney, Melbourne, Brisbane, 
Adelaide and Perth 211,000 (McNair National 
Readership Survey, May-September 1971) 



ELECTRONICS 

Australia 


Incorporating “RADIO, TELEVISION and HOBBIES” and "MODERN WORLD” 


AUSTRALIA’S LARGEST-SELLING ELECTRONICS & HI-FI MAGAZINE VOLUME 34, NO. 3 



Meet Colin Francis, who recently joined our 
company. Mr Francis came to us from Lawson 
Publications, where he was founder Editor of 
the trade journal “Australian Electronics 
Engineering”, and editor of other trade 
publications. At present Mr Francis is on a trip 
to the UK, where he is involved in consulta¬ 
tions with our associated magazines in the 
IPC Electrical-Electronic Press and IPC 
Business Press groups. 


Emergency issue 

Because of an industrial dispute which 
affected the production of newspapers and 
magazines in the Sydney area, this issue of 
“Electronics Australia" had to be produced 
under emergency conditions. We were able 
to maintain the technical content substan¬ 
tially intact but some items and advertise¬ 
ments had to be curtailed or omitted. We 
would apologise to readers and advertisers 
for any inconvenience which might result. 
The printing schedule for subsequent issues 
may be affected but we will do our best to 
minimise delays. 


On the cover 

A number of television servicing organisations 
are already prepared for the introduction of 
colour TV into this country in March, 1975. 
Our cover picture shows Mr Jadk Cardwell, of 
the David Jones service department in 
Sydney, adjusting a prototype colour receiver. 
He is using a Korting colour bar generator 
supplied by EMI (Australia) Ltd. Mr. Cardwell 
has completed a colour TV servicing course at 
Sydney Technical College. 


CONTENTS—JUNE, 1972 


world of electronics and hi-fi 


5 Editorial — Big problems with small orders 
10 The story of the BBC’s external engineering service 
15 Centre Industries making GE diodes 
22 Original “atom smasher” is retired. 

24 4-channel discs, part 2 — a compatible discrete system 

50 Nuclear medicine and the gamma camera 

60 Forum — Aging and musical enjoyment; Receiving licences 


projects and technical 


30 Regulated variable supply using new 1C 

32 Magnetic tape bulk eraser 

36 TV sync and pattern generator, part 2 

42 PA amplifier / mixer features power 1C 

54 The serviceman: Miniature radios - a challenge 

56 Microwaves for radio amateurs, part 2 

65 Circuit and design ideas: 

Simple SW converter — Diode probe electronic thermometer — Diode 
sweep generator — 1C signal Injector — Applications for relay reeds 

69 Home study course, 14: Power supplies 
80 Elementary electronics: A three-channel mixer 
83 Elementary electronics: Ideas worth trying 
100 Product reviews and releases: 

Akal GXC-40D cassette deck — Scientific Electronics 512A power supply 
— A & R Soanar DC-DC converter — Sony TC-440 tape recorder — Weston 
551 radiotelephone — CRC chemicals — Radlonlc construction kit. 


regular features 


18 News highlights 
63 Books and literature: 

Network theory — Electrical experiments — Test Instruments 

85 Record reviews — classical 

91 Record reviews — devotional, popular, jazz 

107 Amateur band news and notes 
NO Answers to correspondents 
111 Notes and errata 


ELECTRONICS Australia, June, 1972 


3 
















Need a transistor array? 

GA3046B 

now manufactured 

in Australia 




3 transistors plus 1 differential pair 
All transistors Vbe matched ± 5 mV 
Operation from D.C. to 120 MHz 
Maximum allowable Tj = 125°C 
Low noise 

14 pin D.I.L. package 
Ex stock deliveries 


PHILIPS 

4 ELECTRONICS Australia, June, 1972 


THE ELCOMA DIVISION 

Electronic Components & Materials 
Philips Industries Limited. 

Sydney • Melbourne • Brisbane 
Adelaide • Perth • Canberra • Hobart 

38.1825 



































EDITORIAL 

VIEWPOINT 



EDITOR-IN-CHIEF 

Neville Williams 
M.I.R.E.E. (Aust.) (VK2XV) 

EDITOR 

Jamieson Rowe 

B.A (Sydney) B.Sc. (Technology, NSW) 
M.I.R.E.E. (Aust.) (VK2ZLO/T) 

ASSISTANT EDITOR 

Philip Watson 

A.M.I.R.E.E (Aust.) (VK2ZPW) 

EDITORIAL STAFF 

Ian Pogson (VK2AZN/T) 

Harry Tyrer (VK2ZHH) 

Dick Levine, B.A. 

George Hughes 
Robert Flynn 
John Horsfield 
Ross Tester (VK2ZVO/T) 

Gerry Nicholson 


ADVERTISING MANAGER 

Selwyn Sayers 

CIRCULATION MANAGER 

Alan Parker 


Big problems with small orders 

In Australia, as in many other countries, it has become increasingly harder in 
recent years to buy electronic components in small quantities. More and more, the 
youngster wanting to buy a few resistors or capacitors for a small project, the radio 
amateur who needs a valve or transistor for his transmitter, and the service 
technician who must have a certain part for replacement purposes have been finding 
themselves at a disadvantage. 

Manufacturers have been finding it unprofitable to supply orders for small 
quantities, and are understandably reluctant to do so. Traditionally it has been the 
function of the wholesale distributor and trade stockist to buy in reasonably large 
quantities and resell in small lots. But in order to cover operating costs such com¬ 
panies must generally major on buying fast-moving components. Slower moving lines 
tend to become either “unavailable” or available only on special order — and this can 
often involve long delays. 

There have been indications in the last few months that this situation is reaching 
crisis proportions. In city areas, high rentals are combining with rising wages to force 
wholesalers and trade stockists to either move to the suburbs, or else restrict their 
business wholly to the supply of complete equipment, systems and packaged kitsets. 

Those who have been based in the suburbs or who have moved there have 
generally found that much of their business must be carried out on a mail order basis, 
due to their less convenient location. Yet here again rising postal costs and wages are 
making it less and less profitable to handle small orders. In some cases, stockists are 
being forced to refuse small mail orders on the grounds that by the time they fiddle 
around with money orders, postal notes and other forms of mail payment, they ac¬ 
tually lose money on the transaction. 

The irony of the situation is that when considered as a whole, “small order” sales 
account for very large numbers of electronic components. Small orders add up to big 
business, a fact that is widely acknowledged in Britain and the US. 

Even the big manufacturers admit that there is a lot of untapped market potential 
here in Australia, in the small order business. Yet the situation continues to 
deteriorate. 

Part of the answer may be to generate more, enthusiasm and activity among 
home constructors and radio amateurs, and if this is the case then surely Electronics 
Australia and our contemporary journals are playing our part. But we can only do so 
much, and I suspect that more is going to be needed if the situation is to improve. 

Perhaps by stirring the matter up here, I will prompt others into coming up with 
some additional answers. 

-Jamieson Rowe 


ON SALE THE FIRST MONDAY OF EACH MONTH 


Printed by Wilke and Company Ltd, of Clay¬ 
ton, Victoria, for Sungravure Pty Ltd, of 
Jones Street, Broadway, NSW. 

* Recommended and maximum price only 

Editorial Office 

12th Floor 235 243 Jones Street. Broadway, 
Sydney. 2007 Phone 2 0944. Postal Address: 
Box 2728. GPO, Sydney 2001. 

Advertising Offices 

Sydney — 8th Floor, 235-243 Jones Street, 
Broadway, Sydney, 2007. Phone 2 0944. 
Sydney representative: Bill Summons. 
Melbourne, — 374 Little Collins Street, 
Melbourne, 3000. Phone 67 7021. 

Melbourne representative: Jeffrey Byrne. 
Adelaide — Charles F. Brown & Associates 
Ltd, 429 Pulteney Street, Adelaide, 5000 
Phone 23 1657. 


Adelaide representative. Tom Duffy. 

Perth — 454 Murray Street, Perth, 6000. 
Phone 21 8217. 

Perth representative: Jack Hansen. 

Representation 

Melbourne — Sungravure Pty Ltd, 392 Little 
Collins Street. Phone 67 7021. 

Brisbane — Sungravure Pty Ltd, 78 Elizabeth 
Street Phone 21 6690. 

Adelaide — Sungravure Pty Ltd, 104 Currie 
Street, Phone 51 3502. 

Perth — Sungravure Pty Ltd, 454 Murray 
Street. Phone 21 8217. 

Newcastle, NSW — Associated Newspapers 
Ltd, 22 Bolton Street, Phone 2 3696. 

London — John Fairfax and Sons (Aust) Ltd. 
Reuter Building, 85 Fleet Street. 

New York — "The Sydney Morning Herald" 
Ltd, 1501 Broadway. New York NY 10036 


Circulation Office 

9th Floor, 235-243 Jones Street. Broadway. 
Sydney. 2007. Phone 2 0944. 

Distribution 

Distributed in NSW by Sungravure Pty Ltd. 
Jones Street, Broadway, Sydney: in Victoria 
by Sungravure Pty Ltd. 392 Little Collins 
Street. Melbourne; in South Australia by 
Sungravure Pty Ltd. 104 Currie Street, 
Adelaide: in Western Australia by Sungravure 
Pty Ltd. 454 Murray Street. Perth, in 
Queensland by Gordon and Gotch (A'asia) 
Ltd: in Tasmania by Davies Bros Ltd. 
Macquarie St, Hobart, in New Zealand by 
Gordon and Gotch (NZ) Ltd. Adelaide Rd. 
Wellington. 

Copyright. All rights reserved. 

Devices or arrangements shown or described 
herein may embody patents. Information is 
furnished without responsibility for its use 
and without prejudice to patent rights 


ELECTRONICS Australia, June, 1972 


5 









,1 



you can 
the quality 

SOUN 

with fine crystal or 


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KL-7080 5-WAY 
6-SPEAKER SYS¬ 
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RMS. Freq. response 25-22,000 
Hz. Free-edge 15" woofer, mid-range 
horn, 5" cone-type mid-range, 2 horn-type 
tweeters and 1 metal cone super tweeter. 


KR-6170 “JUM¬ 
BO” STEREO 
RECEIVER. High 
fidelity with a 
new meaning . . . 
stereo for play¬ 
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listening. Play or 
practice your fav¬ 
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companiment of 
Electronic 
Rhythm Com¬ 
poser which pro¬ 
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rhythms (march, 
rock, ballad, etc.) 
and 5 percus¬ 
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The “actual-sound” reproducers is an accur¬ 
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sound reproduction equipment. You are 
“there” . . . whether your musical preference 
is hard rock or Handel. Kenwood research and 
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on your discs for late-night mood listening or 
auditorium volume—without distortion. For 
unbeatable craftsmanship . . . choose 

Kenwood. 


6 


ELECTRONICS Australia, June, 1972 





















K P - 3 0 2 1 
AUTO TURN¬ 
TABLE. All you do 
is switch on, with 
this 24-pole synchro¬ 
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Smooth, reliable, durable tone 
arm operation. Auto-play, auto¬ 
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automatic. Freq. response 20-20,000 Hz. 




What more could you want in stereo 
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the sound approach to quality 

® KENWOOD 


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ADELAIDE 93 6117 BRISBANE 44 4674 

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CANBERRA 47 9624 c NEWCASTLE 61 4991 

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I 

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To: Jacoby, Mitchell & Co. Pty. Limited 

P.O. Box 2009, North Parramatta, N.S.W. 2151 
Please send me full details on Kenwood 

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□ KR-6170 Stereo Receiver, and location of nearest Kenwood 
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ADDRESS. 

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ELECTRONICS Australia, June, 1972 


7 






























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ELECTRONICS Australia, June, 1972 

































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ELECTRONICS Australia, June, 1972 


9 







































Every day,'the British Broadcasting Corporation transmits over 100 hours 
of radio programs in 40 different languages for reception overseas. The t? 
technical facilities used to ensure adequate reception in the areas to which 
the programs are directed are described in this'Vticle. 


In the greater part of the world radio is 
still in a stage of development brought 
about by the transistor revolution. Compact 
radio sets, with a performance on medium 
and shortwaves which was unthought of at 
such a low price only a few years ago, have 
brought the outside world to the doorsteps of 
ordinary people in even the most remote 
countries. 

It is to meet the challenge of reaching and 
holding this ever-expanding audience that 
the BBC’s External Services are broad¬ 
casting over 100 hours of programs in 40 
different languages throughout the 24 hours 
of each day of the year. The BBC’s External 
Services are not alone in competing for the 
world’s audience, as more than 60 other 
countries or organizations are also 
broadcasting to overseas listeners. 

It is the work of External Services 
Engineering to provide, maintain, and 
operate the technical facilities needed to 
produce the programs and to broadcast 
them throughout the world outside the 
United Kingdom, so that they can be heard 
loudly and clearly in the countries to which 
they are directed. 

This calls for coverage of the major 
population areas of the world for long 
periods each day with transmissions which 
are free from interference and competitive 
in signal strength with the multitude of 
signals from other broadcasting 
organizations. To tarry out this task ef¬ 
fectively requires that the transmitting 
network is planned on a world wide basis 
and uses, wherever practicable, relay 
stations near to the areas to be served so 
that the signals can be as strong as possible. 

In planning the transmitter network, 
account has to be taken of the listening 
habits of the audience, the availability of 
frequencies, the capital and running costs of 
the technical plant, and the present and 
future performance of domestic receivers. 

Before 1950 HF broadcasting was essen- 

IIIIIIIIMMIIMIIMHIIIIIIIMIIIIIIIIIIIMMlilillHMHlillMIIHIHMMHHIIIHIHHMMIIHMIlimilM 

* The author is Chief Engineer, BBC External Broadcasting. 

This article is reproduced from "Sound and Vision Broadcasting", published 
by The Marconi Company, England, by arrangement with the editor. 


continent and the Middle East, and to 
provide short-wave coverage of the more 
scattered land areas such as Africa and 
South America (although in time it is hoped 
to be able to provide a complementary 
medium-wave coverage to some of these 
areas). 

The External Services use a total of 70 
highpower transmitters. Of these 46 are at 
sites in the UK and 24 at relay stations 
overseas. These relays, depending on 
circumstances, are operated either by the 
BBC or by the Diplomatic Wireless Service 
of the Foreign and Commonwealth Office. 
They all, however, broadcast solely BBC 
programs originated in Bush House, Lon¬ 
don, on frequencies and at times scheduled 
by External Services Engineers. 

The main transmitting sites in the United 
Kingdom are at Daventry (Northants), 
Rampisham (Dorset), Skelton (Cum¬ 
berland), Wooferton (Shropshire) and 
Crowborough (Sussex). Wooferton is chiefly 
used for relaying “Voice of America’’ 
programs originating in the United States; 
and Crowborough for broadcasting to 
Europe on medium-wave via its 600KW 
transmitter. 

Of the 46 high-powered transmitters in the 



The interior of the 
receiving station at 
the BBC's Eastern 
Mediterranean re¬ 
lay station, one of 
six relay stations 
located around the 
world. 


tially a medium for broadcasting over very 
long distances. However, during the 60s it 
tended to become a medium for regional 
coverage up to a distance of 3000 miles from 
the transmitting station. This was brought 
about by the desire of the broadcasters to 
simplify their short-wave frequency 
planning. Thus the average listener finds 
some measure of the stability of frequency 
usage to which he has become accustomed 
by medium-wave listening. 

Also, the overcrowding of the short-wave 
broadcast bands and the comparative in¬ 
sensitivity of the cheaper transistor radios 
using short whip aerials, set a need for high 
signal strengths which is most easily met by 
using relay stations within one-hop range of 
the target areas. Relay station development 
has therefore to be balanced between the 
use of medium-waves which all radios can 
receive, but which for the distances in¬ 
volved are limited to night-time use only, 
and short-waves which can give a service 
throughout the 24 hours but are received on 
only a proportion of receivers. 

The aim of External Services has been to 
provide both medium and short-wave 
coverage of concentrated population areas, 
for example, Europe, the Indian sub- 





















United Kingdom. 20 have a power of 250KW 
and the remainder are rated at 100KW. 
Additionally, three 30KW single-sideband 
transmitters are available for use as point- 
to-point feeds to the overseas relay stations. 
Twenty-six of these transmitters are of 
modern design and have been installed 
within the last 13 years. The remainder date 
from^the Second World War and will be in 
need of replacement shortly. 

The signals from the UK transmitters are 
currently reinforced by six relay stations 
located in suitable positions around the 
world. In Europe the External Services are 
relayed in Berlin on both medium-waves 
and VHP. In Asia, the Eastern Relay 
Station, which came into service on June 1 
1969, serves India, Pakistan, Afghanistan. 
Iraq, the Arabian Peninsula and the Gulf 
area. It operates on medium-waves with a 
maximum power of 1500KW and broadcasts 
both the World Service (a 24-hour service in 
English), and vernacular services for the 
areas concerned. 


The majority of these are dual-band curtain 
arrays with gains of around 20dB over an 
isotropic radiator. A proportion of the 
arrays are slewable by ±20° so that they 
can be used to serve important target areas 
off the normal axis of the array. Very few 
rhombic or log-periodic arrays are used as, 
in general, the former have too narrow a 
main lobe for area broadcasting while the 
latter have insufficient gain compared to 
curtain arrays. 

Normally the maximum power used on 
short-waves is 250KW from a single trans¬ 
mitter. However, equipment exists at some 
stations to enable two 250KW trans¬ 
mitters to be combined to give a power 
output of 500KW. The method which is used 
employs separate feeders for each trans¬ 
mitter connected to adjacent halves of 
curtain aerial arrays. Probes underneath 
the array enable the phases in each half to 
be compared, and a DC signal, which can be 
used to control, manually or automatically, 
the phase of one transmitter, is returned to 


watch to be kept on the overall audibility of 
the transmissions, and to identify the origin 
of interfering signals, to indicate any 
corrective action which may be needed. 

The reporting system available to Ex¬ 
ternal Services covers most areas of the 
world and information is received from a 
variety of sources, such as the Overseas 
Relay bases, voluntary reporters, official 
posts and the general public. The total 
number of reports received is very large, 
especially after the introduction of a new 
seasonal schedule. It is quite normal in one 
such week to have 10,000 reports on various 
frequencies from as many as 250 different 
locations. 

In the past this information had to be 
collated manually. This meant that either 
the results were not known until many 
weeks after the introduction of the schedule, 
or could only be sampled with the possibility 
of error if they were to be available in time 
for corrective action to be taken. 

A computer program is now available 



The main transmitting hall at the BBC’s External Services 
transmitting station at Skelton , Cumberland, England . 


The 250KW screened trunk feeders and switching station at the 
Skelton transmitting station. 


The Eastern Mediterranean Relay 
Station operates on medium-waves for .the 
Arabic, Persian and World Services. It also 
relays these and other services on short 
waves to the Middle East and parts of 
Africa, Asia and Europe. The Arabic Ser¬ 
vice is also relayed by a medium-wave 
transmitter in Malta." The Far Eastern 
Relay Station carries, on short-waves only, 
the World Service and most of the Asian 
language services originated by the BBC in 
London for South and South-East Asia and 
the Far East. The Atlantic Relay Station on 
Ascension Island, using four 250KW short¬ 
wave transmitters, broadcasts the World 
Service and vernacular services for most of 
Africa and South America. 

Between all the transmitting sites there is 
a choice of over 400 directional aerials for 
beaming the signals towards the target 
areas for which the programs are intended. 


the transmitter hall. This system enables 
existing feeders to be used and the direction 
of the main beam to be slewed by ad¬ 
justment of the phase of one of the trans¬ 
mitters. The 500KW transmissions are 
normally limited to use on especially dif¬ 
ficult transmission paths, or where in¬ 
terference makes the power necessary. 
Another technique which is extensively 
used is to operate two or more transmitters 
synchronously on the same frequencies with 
each transmitter working into separate 
arrays on different bearings. The trans¬ 
mitters can either be on the same or dif¬ 
ferent sites and often three 250KW trans¬ 
mitters on the same frequency are em¬ 
ployed. 

According to the short-wave schedule 
currently in operation, up to 125 different 
frequencies can be used on any one day. It is 
therefore essential to have a reception 
reporting system to enable a continuous 


which enables all reports to be tabulated 
and collated on either frequency or location 
basis and allows a comprehensive report to 
be made available within a few days of the 
introduction of new schedules. 

All programs are produced or assembled 
in one or other of the 48 studios in Bush 
House from where they are fed by Post 
Office cables or links to the UK transmitting 
sites. The relay stations normally pick up 
the direct UK broadcast signals for relaying 
to their adjacent areas, though in some 
cases direct point-to-point SSB trans¬ 
missions are used to provide additional 
relay facilities. Cable and satellite circuits 
are also used although, due to their expense, 
they are normally limited to periods of poor 
propagation conditions, or for special oc¬ 
casions. 

As an alternative to direct relays about 
20 £ '« of the programs are pre-recorded on 
magnetic tape and sent out by air freight. 


ELECTRONICS Australia, June, 1972 11 














Another great idea from 


INTERDYN 


do it yourself and save! 

(SEAS) 

HI - FIDELITY 
SPEAKER KITS 



This famous Scandinavian manufacturer has come up with an 
appeal to all budget-minded hi-fi fans — acoustic suspension, 
neoprene surround speaker kits which you can fit into your own 
readily made enclosures! 

Ranging from the two-way Type 10 with peak power rating 40W 
to the Type 60 with 4 drive units and peak power rating 120W, 
these speakers have the world-famous smooth response, superb 
transient performance, long throw woofers and matched 
disperion characteristics for which Seas are justly renowned. 

Kits are complete with wiring diagrams and fully detailed 
drawings. If you want to match speakers with your furniture, if 
you have enclosures all ready for speakers, if you want to save 
money, get the facts on the Seas kits! Cabinet sizes 10 litres (1/3 
cubic ft.) to 60 litres (2 c.ft). 


TYPE 10 

e:— ' m 

Two drive units, 6 y 2 " woofer, 114" dome 
tweeter. Frequency range in 10 litre cabinet, 
45-20,000 Hz. Peak power rating 40W. 

\ (SS3>“ 

V \ 

TYPE 18 


Two drive units. 814" woofer, 1/4" dome 
tweeter, Frequency range in 20 litre cabinet, 
35—20,000 Hz. Peak power rating 60W. 


TYPE 30 

Three drive units 10" woofer, 1!4" dome 
tweeter. Frequency range in 30 litre enclosure, 

30 — 20,000 Hz. Peak power rating 70W. 

CUM) H\Gv\-t\mux ft 

—— T 

TYPE 35 

Three drive units 2 x 8!4" woofers, V/ 2 " dome 
tweeter. Frequency range in 40 litre enclosure, 

30 -- 20,000 Hz. Peak power rating 120W. 

TYPE 60 (Kit illustrated) 

4 drive units. 2 x 10" woofers, 1 x 6 " 
mid-range, 114" dome tweeter. Frequency range 
in 60 litre cabinet, 25 — 20,000 Hz. Peak power 
rating 120W, crossover frequency 600 Hz and 

3,000 Hz. 


Available at: Interdyn Agents 

VIC: Encel Electronics, P/L 431 Bridge Rd, 

Richmond, 3121. Tel 42 3762. 

NSW: Encel Electronics Pty. Ltd. 

QLD: Stereo Supplies, 100 Turbot St., Brisbane, 
4000 

S.A.: Challenge Hi-Fi Stereo, 6 Gays Arcade, 
Adelaide, 5000. 

TAS: Audio Services, 72 Wilson St., Burnie, 7320. 


INTERDYN 


Send coupon for literature: 

r 

To: International Dynamics (Agencies) Pty. Ltd. 

P.O. Box 205 Cheltenham, Vic. 3192. 

I Please send information on Seas Speaker kits. 

I NAME.. . . 

I ADDRESS .8564 EA 































U.K. ^ 
STATIONS 


BERLIN 

RELAY 


E. MED. 
RELAY 


C. MED, 
RELAY 


•EASTERN 

RELAY 


FAR ^ 
EASTERN. 
RELAY' 


ATLANTIC 

RELAY 


An approximate coverage diagram of some of the BBC’s overseas relay stations. 


By this means the program quality for less 
topical items can be maintained at a higher 
level than is normally possible via radio 
pick-ups. Nevertheless, relay quality of a 
high order is achieved by the use of 
diversity reception and receivers specially 
modified to reduce distortion while 
retaining good overall audio-frequency 
response. 

The assembly of the language programs 
into streams at networks and their con¬ 
nection at precisely timed intervals to the 
outgoing lines involves a very large number 
of daily switching operations. This results 
from the number of languages broadcast, 
and the frequent changes of transmitters 
which are necessary to make the most ef¬ 
ficient use of the facilities available. • At 
present these switching operations are 
carried out by “Uniselector” stepping 
switches operated back to back. The 
sequence for each seasonal schedule is set 
up manually by inserting markers in the 
switches to identify source, time and 
destination routing. 

This equipment, which has been in ser¬ 
vice for 13 years, is now being replaced by a 
more flexible system which will be con¬ 
trolled by a small computer. The new 
system will allow switching in five-minute 
time blocks instead of the present 15 
minutes and give more flexibility to 
program planning. The use of modern input 
and output peripheral equipment will also 
enable the setting-up' time and staff 
requirements to be reduced. 

Most of the studios at Bush House are 
small and specially designed for the news 
and interview types of program which 
comprise the major part of External Ser¬ 
vices output. A few studios are available for 
music and plays, of which the largest can 
contain an audience of 50 and a small or¬ 
chestra. A recent innovation has been the 
installation of several small studios which 
can be directly operated by non technical 
staff. A feature of these studios is the use of 
a relatively complex compressor / limiter 
amplifier for controlling signal! levels. This 


enables the producer to concentrate more 
on program content than technicalities 
when operating the studio on his own. 

In addition to the direct broadcast 
facilities, studios and equipment are 
available for making transcription 
recordings for distribution overseas, either 
on stereo gramophone records or magnetic 
tape. These recording facilities have been 
built to very high standards and can provide 
complete programs on disc which are equal 
to the best commercial records currently 
available. They are widely used by overseas 
broadcasters for transmission on their local 
radio stations, and have achieved such a 
reputation for artistic and technical ex¬ 
cellence that they are often used as a 
standard for judging the performance of 
broadcasting plant. 

With the studio and transmitting facilities 
now available, it is possible for listeners in 
most parts of the world to receive strong 
signals from the BBC, either in English or 
their own language, during the local peak 
listening periods. A program of capital 
development is planned which, when funds 
are made available, will enable the process 
of modernising facilities in the UK to be 
completed and, by the construction of ad¬ 
ditional relay stations, will improve the 
present reception gaps in Europe, Africa 
and Latin America. 

The possibility of direct broadcasting 
from satellites is kept under review, but 
with present costs and problems of frequency 
and receiver availability, satellites do not 
seem for many years to be able to offer a 
viable alternative to the present system of 
terrestial broadcasting. This is especially 
true when the requirement for broadcasting 
up to six simultaneous transmissions in 
different languages is taken into account. 
Whatever the future holds, the BBC’s Ex¬ 
ternal Services ha-ve both the program and 
technical expertise to meet the challenge of 
reaching and holding the ears of the 
ever increasing audience resulting from the 
universal availablility of transistor radios. 

& 


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ELECTROINCS Australia, June, 1972 13 












how 

on earth could 
you improve the 


&AHSUI AU555A 



With a recommended maximum price of only $237* the 
Sansui AU-555A solid state stereo amplifier offers a great 
deal more to the dollar wise Australian audio enthusiast. 


maximum 


Continuing development by Sansui, Japan’s leading 
audio-only manufacturer, has resulted in a fine stereo 
amplifier with every desirable feature . . . the total 
power output is 60 watts into 8 ohm speaker systems, 
and the frequency response is -1 dB from 20 Hz. to 
40 kHz. at normal listening levels. 


of $287? 


There’s loads more . . . bass, treble and mid-range 
controls, provision for two pairs of stereo speakers, all 
the usual Sansui filter and mode controls . . . 

And here’s the most vital point of all. In terms of 
tonal quality the Sansui AU-555A leaves similarly 
priced competitors a long way behind. Some dedicated 
enthusiasts claim there’s little perceptible difference in 
tonal quality between the AU-555A and the top-of-the- 
line Sansui amplifier, the AU-999. 

However, as selecting a new stereo amplifier is a 
personal matter, you are cordially invited to slip along 
to your favourite Simon Gray franchised dealer. Listen 
to the Sansui AL/-555A critically. See how much more 
total performance Sansui offers — and how much 
more you get for your money. Call in today! 



Simon Gray Pty. Ltd., 

28 Elizabeth St., 

Melbourne 3000. 

Please send me further 
information about the Sansui 
Model AU-555A and the name 
of my nearest franchised 
Simon Gray dealer. 

Name . 

Address. 


Postcode 



DISTRIBUTORS: 

5 u f tr f!! a n ’J!? ep J in9 W A ‘ : slmon Gr *y Pf y ■ Ltd Head otflce: 28 Elizabeth Street, Melbourne. 3000. 
Tel. 63 8101*. Telex: 31904. Sydney Office: 53 Victoria Avenue, Chatswood. N.S.W. 2067. Tel. 
40 4522*. Canberra Office: 25 Molonglo Mall, Fyshwick, A.C.T. 2609. Tel. 95 6526. Adelaide Office: 
301 South Terrace, Adelaide, S.A. 5000. Tel. 23 6219. N.T.: Pfitzner’s Music House, Smith Street, 
J. e J- 3801. Old.: Sydney G. Hughes, 154-158 Arthur Street, New Farm, Brisbane. 
iPP^ArJ 6 ,.', If 22 ; Tas * : K • w - McCulloch Pty. Ltd., 57 George Street, Launceston. 7250. Tel. 
2 5322. W.A. Distributors: Carlyle & Co. Pty. Ltd., 1-9 Milligan Street, Perth. 6000. Tel. 22 0191. 
Sansui equipment is manufactured by: Sansui Electric Co. Ltd., 14-1, 2-chome, Izumi, Suginaml- 
ku, Tokyo, Japan. 



ELECTRONICS Australia, June, 1972 





















General Electric/Centre Industries 
link provides Australian-made diodes 


Three-way agreement brings the technology behind GE’s transient pro¬ 
tected diodes to Australia; at the same time brings new and challenging 
job opportunities for disabled people. 


by JAMIESON ROWE 

As the result of a three-way manufac¬ 
turing and marketing agreement between 
General Electric in the USA and Australian 
General Electric and Centre Industries in 
Sydney, NSW, GE’s highly successful A-14 
series of glass passivated silicon rectifier 
diodes is now being made in Australia< Only 
a few weeks ago the first production quanti¬ 
ties of the devices came from the new 
production line which has been set up at 
Centre Industries’ facility in Allambie 
Heights, a few miles north-west of Sydney’s 
Manly beach. 

Centre Industries is a research, training 
and manufacturing facility operated by the 
Spastic Centre of NSW to train, assist and 
provide effective paid employment for a 
wide range of severely disabled cerebral 
palsied and other physically disabled 
people. Under the agreement with GE in the 
US, they are making the A-14 series devices, 
while AGE are taking care of marketing. 

For AGE the venture means that their 
customers can now be assured of a con¬ 
tinuous supply of the full range of A-14 
series devices, with PIV ratings from 50V to 
1000V at 1A. Local manufacture will also 
give them the ability to compete more ef¬ 
fectively with overseas component makers, 
and the opportunity to expand into export 
markets. * 


But it would be wrong to think that GE 
and AGE are only working with Centre 
Industries for purely commercial reasons. 
Like many others, they are very impressed 
with the way Cl is achieving a humanitarian 
goal while still operating as a viable 
commercial undertaking. 

This is expressed by Bryan Catt, AGE’s 
astute National Manager for electronic 
components: “Centre Industries is a unique 
business enterprise. They are really 
showing the world what disabled people can 
do if they are helped out of sheltered 
workshops and slotted into a more normal 
working environment. We’re proud to be 
working with them.” 

Although Cl have been making elec¬ 
tromagnetic relays and relay sets, switch¬ 
ing modules and other related equipment 
for some time, this is their first venture into 
the fast-moving field of semiconductor 
component manufacture. They are quite 
excited about the prospects. General 
Manager Bruce Hume explains: “We 
believe this contract is providing us with a 
bridge to modern technology, and that it 
will enable us to lift and broaden the em¬ 
ployment horizons which we can offer to 
disabled people.” 


Centre Industries have built a new extension 
to their Allambie Heights plant to house the 
diode line, together with an associated testing 
lab, chemical lab and water purification plant. 
GE provided two experienced production engin¬ 
eers, John Tworek and Bob Denne, to help Cl 
set up the new line. The setting-up took John, 
Bob and Cl staff engineer Rex Torzillo just 
three months, which is very short considering 
the specialised technology involved. Already the 
production yields are impressively high, despite 
stringent GE quality control and reliability 
checks to ensure that the local products fully 
conform to specs. 

For the initial phase, to allow the line to 
be established with a minimum of com¬ 
plications, most of the Cl employees work¬ 
ing on the line have been non-disabled. But 
now that the line is operating smoothly, Cl 
are implementing the second phase of the 
operation — aimed at achieving close to 
50^ participation by disabled employees. 
This is in line with their basic philosophy of 
providing “integrated” employment op¬ 
portunities for the disabled. G-M Bruce 
Hume anticipates that on the basis of their 
previous experience in adapting plant and 
training disabled employees, the 50% 
participation goal should be achieved in 
about six months. 

The three-way link between GE, AGE and 
Centre Industries is working out so well that 
expansion of the operation to cover more 
semiconductor products is already being 
mooted. For those keen to see Australia 
acquire more expertise in modern elec¬ 
tronics technology, this is good news. ® 


ELECTRONICS Australia, June, 1972 


15 

















Address. 


■Phone. 


Postcode. 


DEPT. 572 


Occupation- 

If the career you want is not listed, please nominate it. 


JW3.2231 


COMPUTER PROGRAMMING 

Eight courses to match the rapidly 
expanding demand for computer 
programmers. Write today to ICS 
for details of the complete range 
of popular and approved courses. 


ELECTRONIC ENGINEERING 
TECHNOLOGY 

This course is designed to give a 
thorough knowledge of Elec¬ 
tronic Engineering from both the 
practical and theoretical points 
of view-. A certain amount of in¬ 
struction on radio theory is also 
included. 


BASIC ELECTRONICS 

A short course ideal for those 
wishing to obtain a sound know¬ 
ledge of radio theory and indus¬ 
trial applications of electronics. 


ELECTRONIC TECHNOLOGY 

An extremely comprehensive 
course covering principles, ap¬ 
plication and maintenance of 
electronic equipment in indus¬ 
trial and other fields. Included 
are:— 

Electronic Measuring Instruments 
Electronic Instrumentation 
Radio-electronic Jelemetering 
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Facsimile 


in Electronics, 

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INDUSTRIAL ELECTRONICS 
TECHNICIAN 

A technical level course covering 
basic theories as well as ad¬ 
vanced subjects. Data Process¬ 
ing and. Electronic Computers 
are covered in some detail. 
Among other subjects dealt with 
are:— 

Electronic Welders 
Motors & Generators 
Magnet Amplifiers 
Process Control Systems 
Servomechanisms 
Timing & Control Circuits 


RADIO ELECTRIC TELEMETRY 

An ideal course for those wishing 
to specialise in this field as well 
as for engineers whose specialty 
lies in another area. 

ELECTRONICS MAINTENANCE 

As Industry utilises more elec¬ 
tronic equipment there is an 
increasing number of openings 
in the Electronics Maintenance 
field. This course covers:— 
Electrotechnics 
Electronics 
< Maintenance 


COLOUR TV 

Colour TV is on the way and this 
course has been designed to 
give the trained technician a 
good knowledge of the prin¬ 
ciples. The NTSC and PAL sys¬ 
tems are discussed in detail. 

ELECTRONIC INSTRUMENTATION 
& CONTROL SYSTEMS 

This course has been designed 
for electronic technicians in¬ 
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RADIO TELEVISION SERVICING 

This course can be the starting" 1 
point of a busy, profitable career. 
Students will learn how to install, 
calibrate and keep in repair 
modern radio and television 
cells. No prior knowledge is 
assumed and this is an ideal 
course for beginners. 

ELECTRONIC DRAFTING 

Suitable for those wishing to 
specialise in Electronic Drafting. 
Course covers modem drafting 
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draftsmen wishing to make tran¬ 
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SOLID STATE ELECTRONIC 
TECHNOLOGY 

An advanced course for en¬ 
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wish to advance their knowledge 
of solid state theory and hard¬ 
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latest developments in semi¬ 
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circuiting. 

COMPUTER TECHNICIANS 

Programming is included as well 
as instruction on the technical 
aspects of computers. The 
course is designed to assist tech¬ 
nical personnel concerned with 
the installation, maintenance and 
operation of digital computers. 


FUNDAMENTALS 
OF ELECTRONIC COMPUTERS 

A course designed for both be¬ 
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technicians desiring a fundamen¬ 
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manner. 

TRANSISTOR RADIO AND 
PRINTED CIRCUIT SERVICES 

Ideal for radio engineers and 
those who already have a know¬ 
ledge of valve receiver theory but 
require systematic study of the 
more modern techniques em¬ 
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NEWS HIGHLIGHTS 



Microcircuit to keep drunken 
drivers off roads 


Statistical studies in both the US and 
Australia have shown that at least half of 
the road accident fatalities in both countries 
are related to the drinking of alcohol. 

Concern about drinking drivers and the 
destruction of life and property they cause 
has inspired General Motors to develop a 
device designed to prevent drunken 
motorists from starting their own cars. 


The GM ignition-lock device, named 
Phystester, has the added advantage that it 
hinders motor car thieves even if the keys 
have been left in the car. It also prevents 
people from starting their cars if their 
faculties are impaired by other causes such 
as drugs or illness. 

A laboratory model of the Phystester was 
built and has been under test for some time 


now by GM’s Delco Electronics Division. 
The laboratory model looked promising — 
so much so that its designers decided to 
have the display, response and memory 
storage circuits miniaturised so the unit 
could be installed in a car’s dashboard. 

Under contract to GM, the North 
American Rockwell Microelectronics 
Company, which is primarily an aerospace 
contractor, successfully reduced the hatbox 
full of conventional electronics parts down 
to a piece of silicon roughly the area of the 
head of a match. The large scale integrated 
(LSI) circuit is produced by the company’s 
metal oxide semiconductor (MOS) process. 
NR Microelectronics is the largest 
manufacturer of MOS / LSI circuits in the 
world. 

Containing 4,641 transistors for logic and 
display functions, the MOS / LSI circuit also 
has enough memory storage for a variety of 
electronic lock codes and the five-digit 
numbers that are displayed briefly to the 
motorist. 


How it works 


When installed on a car’s dashboard, the 
Phystester is designed to operate as 
follows: 

(1) After turning the ignition key, the 
driver has to punch five buttons in 
correct order to insert the car’s code¬ 
lock number. The car will not start 
unless its own code-lock number is 
inserted. 

(2) Then the driver punches a “set” button 
causing a random five-digit number to 
appear on the display for a few seconds. 
The driver has to memorise this 
number and punch the correct five 
buttons within a preset time or the car 
will not start. 

Other complications are also being 

considered, such as a secondary signal 

requiring the driver to apply the brakes 
within a preset time. The number sequences 
and secondary signs of driving capability 
are still under study to validate them as 
indicators of a motorist’s ability to drive 
safely. 



Tiny computer memories switch colour at the molecular level. 


Computer memories may shrink even 
more if a newly invented molecular 
memory material proves commercially 
feasible. Thin sheets of the new material, 
patented by US Navy researcher Irwin 
Schneider, should be able to store more than 
10 7 bits per sq cm, as compared to 10 * 1 2 * * 5 bits 
per sq cm for existing disc memories. 

The method of operation depends on the 
optical properties of potassium chloride, 
which is normally a clear crystal, but which 
can be coloured by impurities. A 
potassium ion (K+) is in this case 


replaced by a sodium ion (Na+) and two 
adjacent chloride ions (Cl—) are replaced 
by electrons. 

Dipoles formed by the electron pairs are 
initially all aligned in one direction. But 
when the molecule is hit by polarised light 
at 620nm, the light rotates the electron pair 
about the sodium ion so that it ends up 
perpendicular to its original position. 

The original orientation represents an 
“0” and the perpendicular orientation a “1” 
in the binary code. 


Light at 820nm causes the dipole to 
radiate at 1080nm without disturbing its 
orientation, but the polarisation of the 
radiation will depend on dipole orientation. 
The memory can therefore be read by 
shining a beam of 820nm light on the 
molecule and determining the polarisation 
of the radiated beam. 

Holography is planned as an in¬ 
put output method; the new memories 
would therefore require no electrical 
connections. 


18 ELECTRONICS Australia, June. 1972 




















6 Vim^m R 

wmuk 


mmam, 


NASA’S 210ft space antenna 
near completion at Tidbinbilla 


Australia will soon be the only country in 
the world with two 210ft (64m) space 
communication antennas. The new one at 
Tidbinbilla has been structurally completed 
and electronic components are now being 
installed. 

The 7,000-ton antenna is similar to the 
210ft NASA antenna at Goldstone, 
California, which until now has been 
NASA’s only antenna of that size. Another 
210ft antenna is presently being built near 
Madrid, Spain; the three will support in¬ 
terplanetary missions from 1973 into the 
1980s. 

BIG $A 17,000,000 DISH stands 235ft high in 
the hills near Canberra. Structurally 
complete, it is awaiting installation of 
electronic equipment before going into 
operation in 1973. 



NASA has been borrowing the 210ft radio 
telescope built for CSIRO astronomers at 
Parkes, NSW, for deep space coverage from 
this hemisphere, and has based the design 
of the Goldstone antenna and both new ones 
on the CSIRO design. 

Tidbinbilla’s new antenna is as high as a 
23-storey building and its 210ft dish has a 
surface area equal to 15 tennis courts. The 
shape of the dish must be maintained as a 
perfect paraboloid within + l/8in, a fact 
which accounts for the unusually strong 
framework. 

Like other Deep Space Network (DSN) 
antennas operating at frequencies of 
2100MHz transmitting and 2300MHz 
receiving, the new antenna uses a 
Cassegrain cone feed mounted in the centre 
of the reflector. 

The Cassegrain design is similar to that of 
an optical telescope. Signals reflected from 


PERFECT PARABOLIC SURFACE on an 
immense scale is the problem faced by the 
antenna's builders. Size of the dish can be 
appreciated by comparing it with the size of 
the workmen shown above. The 210ft dish, 
over six times as sensitive as the 85ft an¬ 
tennas, will significantly extend the useful 
life of interplanetary spacecraft. 

the main dish hit a sub-reflector mounted on 
a truss-type support extending outward 
from the main dish. 

The sub-reflector focuses the signal into 
the feed horn of the Cassegrain cone, where 
it is amplified by a maser. 

The maser provides maximum am¬ 
plification with a minimum of added noise. 
To minimise noise, it is immersed in liquid 
helium at —270°C. Signals returning from 
spacecraft are usually amplified about 
40,000 times by the maser, then are fed to 
the main receiver where they are further 
amplified. 

One of the big antenna’s first jobs when it 
becomes operational in mid-1973 will be to 
take over tracking of Pioneer 10, now on its 
way to Jupiter. By that time next year, 
Pioneer 10 will be getting out of range ol 
Tidbinbilla’s 85ft (26m)antenna. The new 
210ft antenna is 6»/ 2 times more sensitive 
than the smaller antenna. 


Resources photos by rocket tested at Woomera 


A Skylark rocket has been launched at 
Woomera to test techniques for high- 
altitude sensing of earth resources. 

The Skylark photographed specially 
selected test areas in South Australia from 
altitudes of between 100-170 miles (170km- 
270km). These areas have been divided into 
sub-areas large enough to register on film 
as having a dominant terrain type. 

The data gathered by the rocket will be 
compared with data gathered on aircraft 
flying at 20,000ft (6100m), and on NASA’s 
earth resources satellite ERTS-A as well as 
information gathered by ground parties. 

The instruments and cameras carried in 
the rocket have been recovered and 
evaluation of the data will be carried out by 
the University of Reading, UK and CSIRO’s 


Mineral Physics Section, Sydney with co¬ 
operation from the South Australian Mines 
Department and the CSIRO Division of 
Soils, Adelaide. 

CSIRO’s interest in this experiment is a 
general evaluation of remote sensing 
techniques, with particular emphasis on 
their use in minerals search. CSIRO will 
correlate the ground, aircraft, rocket and 
satellite data to determine the optimum 
parts of the spectrum for distinguishing 
different terrain types at different altitudes. 

A comparison of the data collected by the 
rocket and by the satellite is expected to 
indicate the optimum sun angle for 
recording ground features and also the best 
time of day for launching remote sensing 
rockets. 


ELECTRONICS Australia, June, 1972 


19 











NEWS 


Cartridge colour TV 
goes into mass 
production 

Winner for the home video replay stakes 
will be decided in the marketplace. Video 
tape cartidges got a boost recently with the 
announcement that the giant US retailer, 
Sears, Roebuck and Co, has decided to 
market the “Cartrivision” system made by 
Cartridge Television Inc. The system, 
shown at right, will go on sale this month in 
Chicago at about $US1600. 

A library of over 850 prerecorded tapes of 
motion pictures and other programs is 
already available. A full-length film will 
rent for about $US3-5 depending on length 
and content. Blank tapes and prerecorded 
programs will be sold by Sears for $US13. 

The system includes a black-and-white 
video camera for “home movie” recordings 
and a 25in colour television console which 
also houses the video tape unit. 

School computer project 
sponsored by IBM 

Thirteen schools in NSW and 17 in Vic¬ 
toria are participating in a school computer 
project launched recently by IBM 
Australia. 

Kits containing printed circuit cards, 
resistors, capacitors and other basic 
components, which make up the circuitry of 
a digital computer, were distributed to 
science teachers and pupils representing 
the schools concerned at ceremonies in both 
states. 

The components, selected from IBM 
machines, will enable the students par¬ 
ticipating in the project to construct a small 
digital computer. 


It is expected that schools will take an 
average of six months to assemble the 
computer, which is not designed for 
practical work but only to demonstrate the 
principles of digital data processing. It can 
add and subtract. 

The project is meant as an ex¬ 
tracurricular activity and not for regular 
class work. It is designed as a group 
exercise in co-operation between students 
interested in electronics, and those in¬ 
terested in engineering construction who 
will build the chassis for the computer. 

A first and second prize will be awarded 
for the best machines in NSW and Victoria. 
The award will be based on construction, 
presentation, original thought in ap¬ 
proaching the task, and the written 
description of assembly procedures. 


Training course in sound 
and lighting for live theatre 

A unique technical training program 
commenced in April when the Ensemble 
Theatre in Sydney began its first course in 
sound and lighting for live theatre. It is 
thought to be the first such course in 
Australia. 

The program is first of all aimed at people 
who wish to make theatrical lighting and 
sound their profession and secondly to 
directors, producers and actors who wish to 
acquire further knowledge in this field. 

The cost to students will be minimal; one 
third of the costs having been met by The 
Australian Council for the Arts and another 
third being absorbed by the Ensemble 
Theatre. 



STYLISH NEW WALL PHONE will soon be 
available to Australian subscribers. Above , 
Mr H. Brooker of AW A, shows the new 
phone to Mr Ngiam Tong, Chairman of the 
Singapore Telephone Board. 


Business briefs... 

• PLESSEY will supply a batch of a new type cartridge tape replay units for studio 
operators at the ABC. Three of the remarkably small-sized units, called Rapid-Q 
Triple-Play, housed in a single cabinet, take up less than 1 / 5 the space taken by 
three conventional cartridge replay units. 

• STC has been awarded a $19M contract to design and install a communications 
network for the 258-mile natural gas transmission system operated by West 
Australian Natural Gas (WANG). The pipeline extends from Perth north to Dongara 
and south to Pinjqjra. 

• ZELLWEGER, manufacturer of ripple control equipment, has just opened a $V 4 M 
factory in Brookvale (Sydney). Ripple control is a system of controlling remote 
switching functions by injecting voice-frequency impulses into the electricity net¬ 
work. The company also markets police radar systems in Australia. 

• DIGITAL EQUIPMENT will computerise CSR’s Victoria and Macknade sugar mills, 
70 miles north of Townsville. One computer will be used for direct control of the 
milling process and a second will be used for production control with data entered on¬ 
line from terminals installed in the two mills. 

• RACAL announced recently that their Milgo 5500/96 Modems, installed at the Data 
Bank Centres in Auckland and Wellington, have achieved the fastest data trans¬ 
mission using voice frequency channels in the Southern Hemisphere. This is the 
first time that 9600 bits per second data transmission has been attempted over 
normal (300-3400Hz) common carrier circuits. 


20 ELECTRONICS Australia, June, 1972 










FC.4923.A 


Fairchild Powet 

Four times before we’ve started 
to make power transistors in Australia. 

Each time, its been less than perfect. 

We’ve had manufacturing problems. 

We’ve had delivery problems. 

We’ve had suitability problems. 

Now we’re making power again. 

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Because this time we’re making 
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And this time the luck’s on your side. 

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FAIRCHILD 


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Vic. 7234131. 

Sydney 4394355. Adelaide 631435. 

Brisbane 978222. Perth 674696. 

Canberra 956811. N.Z. Otahuhu 69299. 

5th time kicky. 

ELECTRONICS Australia, June, 1972 21 








Rutherford’s original “atom 
smasher” is retired 


In a short, simple ceremony in Johannesburg, South Africa, in August of last 
year, the world’s first commercially built “atom smasher’’ was switched off 
for the last time after 34 years’ service in Britain and in South Africa. It is 
the Philips 1 million volt cascade accelerator built in 1937 for the world- 
famous Cavendish Laboratory in Cambridge, England. For the last six years 
it has been the nuclear research “work horse” for the Nuclear Physics 
Research Unit (NPRU) at the University of the Witwatersrand, South 
Africa. 


In its lifetime, it helped to open up the 
whole field of nuclear physics and con¬ 
tributed to Cavendish Laboratory’s fame as 
a world research centre for many years. 
During the second world war, it was used to 
obtain key information for the development 
of the atom bomb. 

The date of the final switch-off marked 
the centenary of the c birth of Lord 
Rutherford, the Nobel prize winner who 
gave science the basic method of nuclear 


research used today. It was Lord Ruther¬ 
ford who ordered the cascade accelerator 
from Philips in Holland, in 1936. 

Lord Rutherford was the first man to 
learn about the structure of atoms by 
bombarding them with high speed particles 
obtained from naturally radioactive 
elements. After some years he found that 
further research required much faster 
particles and some means had to be found to 
produce them artificially. 


22 ELECTRONICS Australia, June, 1972 


Historic cascade generator (left) was 
switched off for the last time by Mr John 
Poot (second from right), Chairman of 
the Philips Group in South Africa, before 
a small audience of South African 
scientists. A similar generator is still in 
operation at the University of New South 
Wales after being moved there from the 
Australian National University in Can¬ 
berra. 

It had been known for a long time that 
charged particles could be accelerated 
electrically, as was done with electrons in 
X-ray tubes. But much greater speeds were 
needed than could be produced by the 
voltages of the x-ray apparatus of the 1930s. 
Two of Rutherford’s assistants, Cockcroft 
and Walton, devised a circuit using 
Greinacher rectifiers stacked up in series so 
that the voltage was doubled for two stages, 
trebled for three and so on. 

After small scale experimental devices of 
this kind had shown that the method was 
practical, Rutherford got Philips of Eind¬ 
hoven to build a machine capable of 
generating a million volts and a current of 
several milliamperes. This machine, the 
first commercially built “atom smasher” 
was installed in the Cavendish Laboratory 
in 1937 and proved successful beyond all 
expectations. There it was in operation until 
1965, when it was moved to South Africa and 
operated successfully until its retirement in 
1971. 

In the veteran machine’s place, the 
NPRU is commissioning a Philips 2 million 
volt accelerator from the Diamond 
Research Laboratory where it has been 
used since 1960 on research into the effect of 
radiation on the physical properties of 
diamonds. Next year, this machine will be 
joined by a giant tandem Van de Graaff 
accelerator producing 12 million electron 
volt protons and higher energies for heavier 
ions, for example, up to 56 million electron 
volts for accelerated oxygen ions. This will 
be housed'in a special building which is now 
rising on the campus. 

The retiring machine was affectionately 
called the “Old Lady.” Officially, it is 
known as “Phoenix” because it had to be 
rebuilt in 1961 when it was acquired from 
the Cavenidsh Laboratory. 

Another very successful cascade 
generator was built for the Australian 
National University in Canberra on the 
order of Professor Sir Marcus Oliphant and 
it was used for many years by his successor 
Professor Sir Ernest Titterton. Installed 
and commissioned by Frank Hornman of 
Eindhoven and Frank Dickson of Sydney, 
the job took three months to the final tests. 

The Canberra cascade was a seven stage 
generator, standing thirty feet high and had 
a nominal output of 1.4 million volts but was 
limited to 1.2 million bj the lower air 
pressure at Canberra which is 2000 feet 
above sea level. Any attempt to go over this 
limit resulted in a spark jumping 18 feet 
onto the roof of the building with a 
deafening bang and the disruption of nearby 
electrical apparatus. 

Like the first of its kind at the Cavendish, 
the Canberra cascade was not finished with 
the end of its time in the old home. It has 
now been reinstalled at the University of 
New South Wales and there it may well 
achieve as long a life as its older sister. ® 





FC.4923.B 


FabthU Powen 

Big chip silicon bimesar power. 

Now made in Australia by Fairchild. 

Now you get more watts for your 
money. High power amplifiers at lower 
cost. Smaller lower cost heat sinks. High 
current, high voltage capability with low 
saturation voltage. Maximum safe area at 
high junction temperatures. Complemen¬ 
tary pairs. And T03, T05, T066 packages. 

For example. 


Max. 

Power 

T.C.25°C 

Product 

Polarity 

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115 W 
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AY8149 

AY9149 

NPN 

PNP 

T03 

T03 

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1.1 V @ 4 Amp 

1.1 V @ 4 Amp 

20-150 @ 4 Amp/4 V 
20-150 @ 4 Amp/4 V 

115 W 
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AY8150 

AY9150 

NPN 

PNP 

T03 

T03 

40 

-40 

1.1 V @ 4 Amp 
1.1 V @ 4 Amp 

20-150 @ 4 Amp/4 V 
20-150 @ 4 Amp/4 V 

35 W 

35 W 

AY8170 

AY9170 

NPN 

PNP 

T066 

T066 

40 

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1.5 V @ 3 Amp 

1.5 V @ 3 Amp 

Typ. 30 @ 3 Amp/4 V 
Typ. 20 @ 3 Amp/4 V 

35 W ' 

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AY8171 

AY9171 

NPN 

PNP 

T066 

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60 

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1.5 V @ 3 Amp 
1.5 V @ 3 Amp 

Typ. 30 @ 3 Amp/4 V 
Typ. 20 @ 3 Amp/4 V 

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2N3054 

NPN 

T066 

55 

1 V @ V 2 Amp 

25-100 @ 2 Amp/4 V 

10W 

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AY8139 

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NPN 

PNP 

T05 

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40 ; 

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b V @ 1 Amp 

Typ 45 @ 1 Amp/2 V 
Typ 35 @ 1 Amp/2 V 

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NPN 

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Typ 45 @ 1 Amp/2 V 
Typ 35 <® 1 Amp/2 V 


Send for our free power brochure. 

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AUSTRALIA PTY. LTD. 

420 Mt. Dandenong Rd., Croydon, Vic. 



ELECTRONICS Australia, June, 1972 23 
















4 ~ Charnel Discs 

Part 2: The CD-4. Compatible Discrete System 


Last month, we discussed at some length the subject of quadraphonic discs 
using the matrix system of encoding and decoding This month we take a 
look at an alternative approach which the proponents pointedly describe as 
a discrete four-channel system. 


by NEVILLE WILLIAMS 


Commercially, the matrix system has a 
lot going for it. Being a 4-2-4 system, it is 
equally applicable to the two-channel disc 
system, a two-channel tape system or to 
FM-stereo broadcasting. The original four- 
channel material can be encoded on to two 
channels, then replayed, dubbed or 
broadcast as such, and finally decoded and 
played back in the home, ostensibly as four- 
channel sound. 

The frequency components involved do 
not fall outside the existing audio pass band, 
so that no special problems of compatibility 
are involved. Matrix-system discs can be 
played back with exising two-channel stereo 
equipment, the signal fed to a decoding unit 
and extra signals made available for am¬ 
plifiers driving the rear loudspeakers. 

Ostensibly, the matrix system offers a 
complete answer to the problem of ob- 
solesence. Enthusiasts can buy matrixed 
quadraphonic records and play them for as 
long as they like on existing two-channel 
stereo equipment, without risk of damaging 
the grooves. At some later date, a decoder 
and additional amplifier channels can be 
added, and advantage taken of the 
quadraphonic content of the records. 

At the same time the decoder provides the 
facility to synthesise extra signals from 
existing two-channel material, so that the 
enthusiast can gain an additional dimension 
from older recordings. 

Reflecting the commercial attractiveness 
of the matrix system, it has no lack of 
support, at least in broad principle. To 
quote from a recent Japanese brochure: 

“Almost all of the four-channel stereo 
systems available on the market today are 


of a matrix system . . .these are listed here 
for reference purposes . 


“Toshiba 

QM system 

Denon 

QX4 system 

Matsushita 

AFD system 

Sansui 

QS system 

Kenwood 

QR system 

Hitachi 

Ambiphonic 

Sanyo 

QSC system 

Mitsubishi 

QM system 

Onkyo 

X—1 model 

SONY 

SQ system 

TEAC 

A—2400 model 

Pioneer 

Quadrilizer” 

JVC / Nivico 

SFCS 


This list does not include manufacturers 
in countries other than Japan, nor does it 
reflect the backing for the system from 
companies marketing complementary discs 
and tapes. 

But, as we pointed out last month, for all 
its convenience and attraction, the matrix 
system falls short in one vital area: it is not 
a true four-channel system nor, 
presumably, can it ever be. 

It suffers intrinsically from cross-talk 
between channels, and individual com¬ 
panies have sought to offset this limitation 
with all manner of electronic processing. 
Whatever the final decoding system 
recovers, it certainly cannot recover four 
original and discrete channels from a two- 
channel medium. 

While the limitations of the matrix system 
will obviously have been well known to 
recording engineers, the implications of 
their mathematics and their rather obscure 
circuitry have not been readily apparent to 


the majority of technical writers. The 
loudest message has been the commercially 
inspired one that the four-channel disc 
problem had been solved by the matrix 
system (albeit rather mysteriously) and 
that it was all over bar the shouting! 

Gradually, however, the contrary opinion 
has filtered through, along the lines ex¬ 
pressed in our last issue — though not in 
anything like as much detail. 

A recent issue of J.E.I. (Japan Electronic 
Industry magazine) carries an article 
headed: “4-Ch. Stereo Systems Pushed 
Strongly, But Lack True Definition, 
Development”. 

Discussing the subject, the writer says: 

“Among the records already on the 
market, those with more echo components 
and recordings of actual performances may 
well be called the matrix records, because 
most matrix records are more befittingly 
described as variations of two channel 
records, rather than four-channel records”. 

One of the companies which has taken a 
strong contrary line in the four-channel 
arena is JVC / Nivico — JVC standing for 
Japan Victor Company. In a recent 
publication, one of their writers says: 

“Separation is incomplete in a matrix 
system. Thus a 4-channel record is not very 
different from a prior stereo record. It is 
advantageous from the standpoint that a 
conventional stylus and cartridge can be 
used without modification. However, it has 
a problem in the complete separation of the 
four sounds, which is the most important 
requirement for 4-channel stereo systems. 
It is not possible by the matrix system to 
pick up one sound alone.” 


SOUND GROOVE 



Fig. 1: The CD-4 system uses the basic geometry of two-channel 
stereo but records signals up to 45kHz on each groove wall. This 
allows two distinct signals to be virtually "stacked " on each wall ' 
one recorded directly at audio frequencies , the other modu¬ 
lated on to a 30kHz carrier , as shown at left. 



ELECTRONICS Australia, June, 1972 


24 






















MATRIX 

CIRCUIT MIXER RECORDING AMP 



CD-4 REPRODUCING UNIT 


(CH1+CH2) + (CH1-CH2) 


(CH3+CH4) + (CH3-CH4) 


FILTER AND 
DEMODULATOR 


MATRIX 

CIRCUIT 


2 


CD-4 

CARTRIDGE 


CD-4 RECORD 


TT 


RECORD PLAYER 


CD-4 AMPLIFIER 


n> <r 


_5 


Fig.3: Playback recovers the sum and difference signals. The latter 
are demodulated back to audio frequencies, then matrixed or 
combined in suitable phase and amplitude to isolate the four 
original and discrete inputs. See text for the simple algebraic 
expressions involved. 


JVC has, in fact, done the lion’s share of 
research into systems which hold real 
promise of a true four-channel capability — 
as expressed in the capacity of a system to 
produce sound from any one of four loud¬ 
speakers in isolation, or from any number 
of those loudspeakers in any desired 
proportions. 

With four-track tapes it is no great 
problem. With discs it is a problem because, 
fundamentally, a stylus can only respond 
reasonably to two vector forces, displaced 
from each other by 90 degrees. It is a 
question of making those two vectors do 
four jobs. 

The system finally adopted by JVC 
assumes the use of a normal stereo groove, 
with each wall at 45 degrees from the 
horizontal. However, instead of each wall 
carrying just one audio signal (right 
channel or left channel) each carries two 
distinct signals, impressed simultaneously 
by the recording cutter. But unlike the 
matrix system, they do not share the same 
frequency band. 

One of the signals is at audio frequencies 
in the range nominally between 30 and 
15,000Hz. 

The other, having first been frequency 
modulated on to a 30kHz carrier, occupies a 
range of frequencies between 20,000Hz and 
45,000Hz — ie 20 to 45kHz. To invoke an old 
PMG term, they are “stacked” in terms of 
frequency. 

Each wall of the groove thus carries a 
complex pattern of frequencies ranging 
from about 30Hz to about 45kHz, 
representing the content of two separate 
and distinct audio signals. Between them, 
the two groove walls carry information 
about four separate audio signals, (see Figs 
1 and 2). 

The playback cartridge can be designed 
along broadly conventional lines but it must 
be capable of responding to tjiis very wide 
frequency range without prominent peaks, 
troughs or resonance effects. In broad 


terms the frequency capabilities need to be 
about two-to-one up on existing high quality 
stereo cartridges. 

The complex pattern of frequencies 
recovered by each half of the cartridge is 
fed to a frequency dividing network. (Figs 3 
and 4). 

Frequencies in the range 30Hz to 15kHz 
are separated out, to become one of the 
signals originally fed to the corresponding 
coil of the recording cutter. 

Frequencies in the range 20kHz to 45kHz 
are likewise separated out, fed to an FM 
demodulator, and thus used to recover the 
second signal fed to that cutter coil. 

From the two groove walls and from the 
respective halves of the cartridge, four 
separate signals are thus obtained. 

At first glance, one might assume that the 
stereo signals for the front loudspeakers 
would be recorded on the respective walls 
as the basic audio component. Further, that 
the stereo pair for the rear loudspeakers 
would be impressed on the 30kHz carriers. 
But in fact, for a variety of reasons, JVC 
have chosen not to do it this way. 

Instead, they matrix (or combine) 
channel 1 and channel 2 together and in¬ 
scribe the resultant “sum” signal as the 
basic audio pattern on one wall of the 
groove. Channel 3 and channel 4 are in¬ 
scribed on the other wall. The logic of this 
approach is not hard to discover. 

If we assume that channel 1 is front left 
and channel 2 is rear left, the sum of the two 
(Ch.l + Ch.2) representing the total left 
signal ends up as the basic audio pattern on 
one wall of the groove. 

Similarly, the total right-hand signal ends 
up as the basic pattern on the other wall of 
the groove. 

If played on a two-channel stereo system, 
the disc is heard as a two-channel stereo 
disc, with normal separation between left 
and right but, of course, with front and back 
combined. 

If played in mono mode, the components 


add again, to produce a normal mono 
signal. 

What of the high frequency components, 
which are also inscribed in the groove 
walls? 

Very simple. 

The majority of styli and cartridges will 
not respond to them very effectively, and 
they will be further attenuated by the 
normal de-emphasis and tone control cir¬ 
cuitry. What is left, still has to get through 
the loudspeaker. Last but not least, 
frequencies above 20kHz are outside the 
range of hearing anyway! 

In this respect, therefore, the discs can be 
accepted as playable on, and compatible 
with, existing stereo and mono equipment. 

What is actually modulated on to the two 
high frequency carriers is the “difference” 
between the respective pairs of signals. The 
same groove wall which carries (Ch.l + 
Ch.2) as a direct audio signal, also carries 
(Ch.l — Ch.2) modulated on to its 30kHz 
carrier. 

In four-channel mode, it is necessary to 
recover and demodulate the 20kHz to 45kHz 
components to isolate the audio difference 
signal (Ch.l — Ch.2). Then by adding 
samples of the sum and difference signals in 
suitable amplitude and phase, the in¬ 
dividual components can be recovered. The 
algebra is very simple: 

(Ch.l -F Ch.2) + (Ch.l — Ch.2) =2x Ch.l 
Again: 

(Ch.l -I- Ch.2) —(Ch.l — Ch.2) =2 x Ch.2 

In short, the Channel 1 signal and channel 
2 signal can be recovered, substanitally in 
their original form. 

The same applies to channels 3 and 4. 

Because it is theoretically possible by 
these means to record and recover four 
completely separate audio signals, JVC 
have called their system “CD-4” standing 
for “Compatible Discrete 4-Channel”. 

The various steps in the CD-4 system are 
illustrated in the accompanying diagrams, 


ELECTRONICS Australia, June, 1972 25 






































































NOHMMIMBLE: 
JVC CD-4 DISCRETE 
4-CH4NNEL RECORDS 



For your free booklet write to:— 

Hagemeyer (Australasia) N.V. 

P.O. Box 49, 

Kensington, N.S.W. 2033 


NIVICO 


World’s first discrete 4-channel records 
now at all JVC dealers 

Hear Bizet’s fiery Carmen Suite and your 
favorite themes from the movies like you've 
never heard them before at your nearest 
JVC dealer. These are the first in many 
planned JVC discrete 4-channel record re¬ 
leases in the coming weeks and months. 

Your dealer has all the facts on the 
records and on the simple add-on equip¬ 
ment you'll need to hear them. If you 
can’t find a JVC dealer in the phone- 
book, write to the nearest JVC distri¬ 
butor listed below for your dealer's 
name and address. 


The missing link in 4-channel 
sound 

Until now the only discrete 4-channel 
sources available were tapes and 
cartridges. Prohibitively expensive in 
themselves for most people, these 
sources also required special 4-chan¬ 
nel decks for playback. The discrete 
4-channel disc —the biggest 4-chan¬ 
nel source of all —was missing. Today, 
thanks to JVC, this is no longer true. 


Big breakthrough in recording 

How to put four separate signals on 
the walls of the standard v-shaped 
record groove while maintaining the 
same tonal quality and price factor of 
existing 2-channel records was a major 
obstacle to the development of the 4- 
channel record. JVC solved it by major 
breakthroughs in the record cutting 
process. So far, some ninety patents 
have been applied for in the JVC CD-4 
system. Some of the breakthroughs 
include a modulated recording system, 
low speed cutting, carrier level control, 
Neutrex process, automatic noise reduc¬ 
tion system and new Shibata stylus. 


Equipment needed 

Other than a basic 4-channel repro¬ 
ducing system and quality turntable, 
the only equipment you need to 
hear JVC discrete 4-channel records 
are the JVC 4MD-10X 4-Channel/2- 
Channel Playback Cartridge and 
JVC 4DD-10 Disc Demodulator. This 
equipment is now available at all 
JVC dealers. 


Discrete 4-channel sound 

Discrete, by definition, means that where 
a plurality of sound transmission systems 
is present, each transmission system is 
independent. This is the JVC CD-4 sys¬ 
tem. It gives the kind of separation which 
makes it possible to orientate sound to 
a required location. And to reproduce 
the original musical properties re¬ 
corded. And to give the listener more 
freedom in movement in listening to 
the music. Matrix-type or encoded 4- 
channel systems do not have this 
complete separation. Which means 
that no matter how sophisticated, 
they just can’t qualify as real high 
fidelity systems. 


CD-4 SECTION, AUDIO EQUIPMENT DIVISION. VICTOR COMPANY OF JAPAN, Shimotsuruma. Yamato City, Kanagawa Pref., Japan 
VICTOR COMPANY OF JAPAN, LIMITED. 1, 4-chome, Nihonbashi-Honcho, Chuo-ku, Tokyo, Japan 
Distributor: Hagemeyer (Australasia) N.V. 59 Anzac Parade Kensington N.S.W. 2033 
Branch Offices: Melbourne, Adelaide, Brisbane, Perth, Lae, Rabaul, Port Moresby, Madang 

26 ELECTRONICS Australia, June, 1972 










which should be studied together with the 
explanatory captions. 

While the foregoing sets out the basic 
principles of the CD-4 system, a perusal of 
JVC literature points up numerous 
refinements in detail and approach which 
represent the difference, no doubt, between 
a basic concept and a commercially ac¬ 
ceptable end result. 

A single master oscillator is used as the 
high frequency source. Its output is split 
and each signal passed separately through 
a “Serrasoid Frequency Modulator”, for 
the respective groove walls. This and other 
precautions in the modulation and 
demodulation process are aimed at 
minimising the generation of spurious beats 
between the respective high frequency 
signals. 

Special attention is paid, not just to the 
deviations of the recorded groove, but to the 
path which is likely to be traced by a 
spherical-shouldered playback stylus. This 
must be related in turn to amplitude and 
frequency, and also to wavelength, as af¬ 
fected by the diameter of the particular 
groove. 

To this end, the signals on the master tape 
are read by separate heads just ahead of the 
heads which feed the recording stylus. 
These pre-record signals are analysed from 
instant to instant, correlated with the 
groove diameter and used to modify 
dynamically the input to the cutter. It is, in 
fact, an extension of the long established 
JVC / RCA Dynagroove technique. 

JVC stress that it is necessary to 
minimise tracing aberrations, both to 
minimise distortion as such and to preserve 
optimum phase relationships in the high 
frequency modulation components. Also at 
stake is the matter of intermodulation and 
cross-talk which can be deteriorated by non- 
linearities in the system. 

JVC diagrams indicate the use of FM pre¬ 
emphasis, compression and expansion, and 
muting — all ostensibly aimed at achieving 
the highest possible signal / noise ratio. 

Interestingly enough, the master disc is 
cut at less than half speed, with master tape 
speed and master oscillator frequency 
scaled down in proportion. This is regarded 
as an interim technique, however. 

In all, something like 90 patents have been 
taken out on various aspects of the system. 

Draft standards have been presented to 
the Japan Record Association, to the El A 
and RIAA in the USA, and to the European 
DIN Standard Committee, with a view to 
encouraging the adoption of the CD-4 
system as a world standard. 

JVC specifications claim that it is ap¬ 
plicable to 12in, 33rpm discs and 7in 45rpm, 
if need be. Frequency response of each 
channel is claimed to be 30Hz to 15kHz, 
cross-talk between channels better than 
25dB, and signal /noise ratio better than 
50dB. These figures apply to what is on the 
disc and to be realised in practice, assume 
the use of a suitably high quality stylus, 
cartridge and demodulator / decoder. 

While Panasonic / National and RCA 
gave the CD-4 system their formal blessing 
and cooperation, JVC / Nivico was the first 
to move it into the commercial sphere with 
the release of about fifteen albums in mid 
1971 straddling the range from rock to 
classical. 

At a press conference in New York, about 
the same time, the President of RCA 
Records, Rocco Laginestra, acknowledged 


MATRIX SOUND IN 
THE LISTENING ROOM 


It’s all very well to talk about the theory of matrix type quadraphonic 
sound and to discuss its merits and de-merits relative to the CD-4 
system described in these columns. But how does the matrix system 
actually sound in the home? Is it likely to satisfy listener requirements? 


The differences between the matrix 
system and the discrete system have been 
explained in detail. Time alone will tell 
whether industry and the public will opt for 
the convenience of one or the theoretical 
superiority of the other. 

While I have been writing these articles, I 
have been living alongside a system 
assembled temporarily from components 
submitted recently for inspection: 
RECORDS: Astor 4-channel, as advertised 
last issue, page 40. Also pre-release 
pressings from Festival, from the Enoch 
Light stable. 


The Onkyo amplifier has facilities for 
adjusting left-right balance and front-back 
loudness. By using the controls to isolate the 
sound sources, the normal left-right frontal 
stereo content is obvious. What comes from 
the rear loudspeakers is much closer to a 
mono signal, but lacking a firm image — 
doubtless due to manipulation of the 
relative phases. 

The overall result — which is what really 
matters — is a room filled with sound. No 
matter where one sits, there is a sense of 
dimension, without, however, a strong sense 
of direction. It is a pleasant effect, if not very 



CARTRIDGE: Empire 1000ZE/X as 
reviewed in March, 1972. This is a very good 
cartridge indeed. 

PLAYER: Garrard Zero 100, reviewed in 
April, 1972. Tracks and operates quite 
happily at 1 gram, even with warped discs. 
Lives up to its specifications in everyday 
use. 

AMPLIFIER: A new model, the Onkyo 4- 
channel Surround Stereo Receiver Y-3A, as 
pictured. It has an in-built matrix to cope 
with quadraphonic matrix discs or to 
simulate four channels from two. It was 
made available to us by Dodwell Trading Pty 
Ltd, 8 Glen St, Milsons Point, 2061. 
LOUDSPEAKERS: Fouf good quality 
bookshelf-size units. 

Having, for some time, lived with 
simulated 2-4 quadraphonic achieved 
purely with additional loudspeakers, I found 
it interesting to compare those results with 
what is obtainable from the abovemen- 
tioned system. 

I can state without equivocation that the 
spread of sound from the matrixed recor¬ 
ding and system is well ahead of what can be 
achieved by 2-4 simulation. The rear signal 
is full bodied and one which could be 
listened to in its own right. 


definitive. My tip is that the majority of 
listeners will clearly prefer it to two-channel 
stereo, just as they have preferred two- 
channel stereo to mono. 

Could it suffer by comparison with the 
CD-4 system? In terms of definition, yes. But 
do listeners really want to be assailed by 
discrete sounds from any quarter of the 
compass? Are they going to react to atmo¬ 
sphere or technology? 

If atmosphere, the matrix can provide it. If 
technology, then the CD-4 system will win. 

And what of the Onkyo 4-Channel 
Surround Stereo Receiver? Well we didn't 
put an instrument near it; we simply took it 
home and used it as described! 

It worked fine. Adequate gain and power 
output, no noise or hum, simple to operate, 
and with all controls doing exactly what they 
were supposed to do. It did a good job 
simulating four channels from two, yet it 
also provides four inputs to cope with 
signals from a discrete tape system or a CD- 
4 decoder / demodulator. 

For good measure, it provided a fine AM 
tuner and a stereo FM tuner, although sad 
to say the latter is wasted in this country. 
Recommended retail price of the Y-3A is 
$319. (W.N.W.) 


ELECTRONICS Australia, June, 1972 


27 














General Electric 

glassivated 

rectifiers 


The reliable 
rectifier 

1-amp (A14) 

MADE IN AUSTRALIA 


The best way to assure reliability in a low- 
current rectifier pellet is to put it in a 
package that really protects it. Protects 
it from shock, humidity, vibration and 
temperature. 

And that’s just what we do with General 
Electric’s glassivated 1-amp (A14) and 
3-amp (A15) rectifiers. Solid glass pro¬ 
vides passivation and protection of the 
silicon pellet’s P-N junction—no organic 
material is present within the hermetically 
sealed package. In addition, rigid mechani¬ 
cal support and excellent thermal character¬ 
istics are provided by the dual heat sink 
construction. 


AUSTRALIAN GENERAL 
ELECTRIC LIMITED 

86-90 BAY STREET, ULTIMO. PHONE 212-3711 

DISTRIBUTORS: 

Fairchild Australia Pty. Ltd., Melbourne, Tel: 723-4131; Sydney 
Tel: 439-4355. 

Watkin Wynne Pty. Ltd., 32 Falcon St., Crows Nest. Tel: 43-2107. 
PB Components, Melbourne, Tel: 53-2766 
GEC-Elliott Automation, Sydney, Tel: 439-1922. 

GEC-Elliott Automation, Melbourne, Tel: 387-2811 
GEC-Elliott Automation, Adelaide, Tel: 71-7971 
GEC-Elliott Automation, Brisbane, Tel: 32-0441 
H. Rowe & Co. Pty. Ltd. Perth, Tel: 28-5444. 


GENERAL ELECTRIC 





“phenomenal progress’’ during the 
preceding few months and indicated that 
RCA was involved in concentrated research 
which should lead up to its own launch in the 
near future. 

Panasonic was in much the same 
situation. 

In fact, the RCA marketing effort is now 
rolling and, by the time this issue is in the 
hands of readers, four-channel discrete 
records carrying the RCA label should be orv 
sale in American record shops. 

RCA’s marketing ultimate plan is to 


How may times can CD-4 grooves be 
played with suitable equipment before the 
fine serrations become noticeably 
degraded? 

What will happen to a CD-4 disc if it is 
played even once with a too-heavy, not- 
very-compliant cartridge? Will the vital 
difference signal simply be obliterated? 

JVC state that research has shown that 
the average LP disc is played about 20 to 30 
times. They appear to be confident that 
their current production will meet this 
requirement easily enough, provided they 


groove wall. However, viewed from the 
front, the Shibata stylus is more pyramidal 
in shape, with a larger effective curvature 
of the surfaces resting against the walls 
parallel to the modulation (Fig. 5). JVC 
claim that the effective area in contact with 
the groove wall is multiplied by four times, 
resulting in less deformation and much 
lower wear of both record and stylus. 

In addition, they claim a marked im¬ 
provement in frequency response and a 
reduction in cross-talk characteristics. 

While the Shibata stylus is aimed at 


MATRIX 



Fig.4: The essential elements of a CD-4 demodulator unit. Output from the pickup is fed 
into the input terminals, left. Audio components, representing the sum signal pass through 
a low pass filter (LPF), while the difference signals have to be separately demodulated and 
processed. They are finally combined in a matrix to produce 4-channel discrete channels. 



Fig. 5: Viewed from the front , the shoulders 
of the Shibata stylus have a larger radius of 
curvature than the conventional elliptical or 
bi- radial type. Pressure per unit area is 
reduced, as also is stylus and groove wear. 

release new records only in the CD-4 
format, thereby eliminating the need for 
double stock inventories. They would be 
played in mono, two-channel stereo or 4- 
channel stereo, according to the buyer’s 
own equipment. 

Despite the confidence and influence of 
the JVC / RCA / Panasonic group, the CD-4 
type of disc yet has to prove its commercial 
superiority over the simpler, though less 
ambitious matrix type. 

In two areas at least, it faces an obvious 
disadvantage. CD-4 discs cannot, as yet, be 
broadcast directly over stereo / FM 
stations, because the frequency content 
exceeds what can be contained in the 
authorised spectrum. 

Again, the CD-4 signal cannot be handled 
by ordinary audio circuits or dubbed for 
ordinary 2-channel tape replay, because of 
its 45kHz bandwidth. 

Of more immediate importance to high 
fidelity enthusiasts is the durability of the 
high frequency signals inscribed in the 
groove. c 


are played with a suitable cartridge and at a 
playing weight no greater than 2 grams. 

They stress, however, that the records 
can be damaged by older and heavier 
cartridges. The “sum” signals would 
remain as normal stereo, but the “dif¬ 
ference” signals, necessary to re-create the 
rear channels, would be at hazard. 

One of the reasons for RCA’s hesitancy 
was reportedly their need to be assured that 
the records would be good for at least 100 
playings under proper conditions, and less 
liable to damage in other circumstances. 

RCA’s answer seems largely to be in the 
choice of a new and harder grade of vinyl. 
Supply and processing problems had to be 
straightened out but the new vinyl is now 
said to be giving much harder pressings 
with lower noise than the standard item. 

When teamed with a new decoder 
developed by Lou Dorren of Quadracast 
Systems Inc, of San Mateo, California, the 
new records are credited with adequate 
difference signals even beyond 100 plays. 

And, finally, JVC research into the CD-4 
technique has produced a new type of 
stylus, which is claimed to represent a 
notable improvement on the current 
elliptical or bi-radial types. 

In these conventional types of stylus the 
combination of the two effective radii 
produces a minimum area of contact bet¬ 
ween the stylus shoulders and the groove 
walls. However, this produces wall 
deformation which can exceed the elastic 
limit of the vinyl with playing weights in 
excess of 2 grams. 

In addition, it is claimed that the depth of 
penetration of the shoulders into the wall 
modifies the mechanical impedance of the 
system and makes it that much more dif¬ 
ficult to achieve extended frequency 
response. 

The new “Shibata” stylus still has small 
radius shoulders, in order to trace more 
effectively the smallest wavelengths in the 


solving problems in the region above about 
15kHz, it will be interesting to see whether it 
will have an impact on the ordinary two- 
track stereo market. 

But, of course, the big question is not the 
Shibata stylus. It is the CD-4 system itself. 
Will the hi-fi fraternity insist on true four- 
channel capability or will it settle for 
something somewhat less pretentious? The 
matrix system, for example? ® 



Specifications: — 

CRT: 3KP1(F) 

Vertical Deflection: 

Sensitivity: 50mV/cm; 

Attenuator: 1/1, 1/10, U 100 with fine control; 
Bandwidth: DC : DC to 1MHz at —3dB, AC : 2Hz to 
1MHz at —3dB, Input Impedance: 2 megohms 
paralleled by approx 30pF. 

Horizontal Deflection: 

Sensitivity: 3V/ cm; Bandwidth: 1Hz to 400kHz at 
—3dB; Input Impedance: 4 megohms paralleled 
by approx 35pF. 

Time Base: 

Sweep Frequency: 10Hz to 100kHz in 4 calibrated 
steps. 

Synchronization: Internal (plus) 

Power Requirements: AC 100/ 117/ 230V 50/ 60Hz 
46W 

Dimensions: 146mm (W) x 213mm (H) x 360mm 
(D) 

Weight: 6.7kg. 

Price $118 plus sales tax. 

PARAMETERS PTY. LTD. 

Available: — 

SYDNEY 439 1601 
MELBOURNE 90 7444 
ADELAIDE 51 671? 

NEWCASTLE 61 4321 Hunter Engineering 
WOLLONGONG 4 0278 Hundell Engineering 
BRISBANE 78 5422 Martin Martens Pty Ltd. 


ELECTRONICS Australia, June, 1972 


29 










































































Variable regulated 

supply using new 1C 

Here is a new variable regulated power supply which would be ideal for 
experimenters, service technicians and development engineers alike. 
Although very simply built and low in cost, it offers a standard of per¬ 
formance normally found only in costly commercial supplies. Heart of the 
unit is a new power regulator 1C from Motorola. 

by GEORGE HUGHES 


A variable low-voltage power supply is 
almost essential for servicing, ex¬ 
perimental or development work on solid- 
state circuits. And if the work is at all 
serious, the supply should ideally be 
regulated — ie, once the output voltage is 
set to a certain figure, it should be main¬ 
tained as closely as possible despite 
changes in the current drawn by the load 
circuit and the voltage of the power mains. 

Until only a few months ago, such power 
supplies have tended to be fairly complex, 
and relatively costly — see, for example, 
our Lab-Type Power Supply of September 
1968. But the complexity and cost barriers 
have now been broken with the development 
of new power regulator integrated circuits 
such as the MC1469R device recently 
released by Motorola Semiconductors. 

Although it costs only a few dollars, the 
MC1469R provides just about all of the 
circuitry needed to produce a high- 
performance variable regulated supply: 
reference source, comparator, regulator, 
current monitoring and overload protec¬ 
tion, and provision for remote sensing. 
Apart from the IC itself all that is basically 
needed is a power transformer, rectifier 
and filter electro, together with a few minor 
components including a pot to adjust the 
output voltage! 

As you can see from the circuit diagram, 
we have actually taken the idea a little 


further than this. Our supply incorporates 
such additional niceties as a case, a power 
switch and pilot lamp, some terminals and a 
low-cost meter to monitor output voltage. 
The resulting unit is still very simple and 
easy to build, and costs a fraction of the 
price of comparable commercial supplies. 

How well does it perform? Here are the 
figures. Output voltage is adjustable from 
3.5V to 20V, the maximum being deter¬ 
mined by the power transformer we were 
able to use, rather than the IC. Maximum 
output current for regulated output voltage 
is 400 milliamps at 15V output and below. 
Above 15V output the maximum current for 
good regulation falls below this figure, 
again largely because of the power trans¬ 
former. 

Voltage regulation at 15V for full 400mA 
loading is .03%, a figure which compares 
very favourably with many high-priced 
commercial supplies. Regulation at 10V is 
almost as good, at .04%. Below this the 
performance drops slightly, but at 5V 
output it is still better than 0.2%. These 
figures are for 240V mains input, but even 
with our DVM we were not able to detect 
supply output voltage variations when the 
mains input was varied up and down by 
10 %. 

The supply is overload and short-circuit 
proof. At a current level a little above 
400mA it changes smoothly into a constant- 


CZl—. 




* 


| 

4 


\ ^ 



^ POWER MATE 


POWER 

OUTPUT 


♦ Q • 

f * 



current mode, the voltage falling to zero at 
about 430mA. It is therefore ideal for bench- 
top use, where the output can often be 
shorted by leads touching or the connection 
of faulty equipment. Current sensing for the 
protection function is performed by the 1.5 
ohm resistor and the BC107 transistor. 

Ripple output of the supply is low. At load 
currents of 150mA and below it is less than 
0.6mV, while at full load of 400mA at 15V 
output and below it is still less than 2mV. At 
ouput voltages above 15V the ripple rises 
above 2mV for load currents above 200mA, 
but this is due to the drooping regulation of 
the power transformer. 

The supply is housed in a small in¬ 
strument case. For the prototype we used 
one of the vinyl covered “ATC” cases 
available through Watkin Wynne Pty Ltd, 
measuring 7in x 5in x 4in (178mm x 125mm x 
100mm). Other ready-made steel or diecast 
cases would be equally suitable. 

The MC1469R uses high-gain silicon 
transistors, and thus like other linear ICs it 
tends to be a little critical of wiring layout. 
A poor layout can result in serious in¬ 
stability problems. For this reason we have 
designed the main section of the supply on a 
printed wiring board, and we strongly 
suggest that you build up the supply using a 
board made from our pattern. Ready-made 
boards should be available shortly via the 
usual suppliers, or if you wish to make your 


THE PARTS NEEDED TO BUILD IT 



Apart from the transformer and rectifier, 
most of the supply wiring is on this small 
printed wiring board. The board is sup¬ 
ported by the power IC, which is mounted 
on a heatsink bracket as shown in the 
photograph on the opposite page. 


1 Instrument case (see text). 

1 Power transformer, 30VCTat 500mA or 
more. 

1 MC1469R integrated circuit (Motorola). 

1 BC107. BC207 or BC147 transistor. 

2 BY 126-50, SD4005, EM4005 or similar 
silicon diode. 

1 Neon indicator bezel. 

1 Small instrument knob. 

1 Miniature single pole ON/OFF toggle 
switch. 

1 Printed wiring board, 72/ps6. 

1 0-lmA meter, preferably with "0-25 
volts” scale. 

1 50k potentiometer, linear. 

1 18k Vzwatt resistor 

3 6.8k V 2 watt resistors 

1 1.5 ohm Vi watt wirewound resistor. 

1 2200uF 35VW electrolytic capacitor. 


1 5uF 25VW electrolytic capacitor. 

1 0.1 uF 25V ceramic capacitor. 

1 0.001 uF 25V ceramic or polystyrene 
capacitor. 

2 terminals, 1 red, 1 black. 

1 Mains lead with 3-pin plug, cable clamp. 
Tagstrips or tagpanel, nuts, screws, 
spacers ( l /sin Whit or 6BA), hookup wire, 
rubber feet, carrying handle, rubber 
grommet, scrap 18 gauge, aluminium for 
heatsink, etc. 

Note: Resistor wattage ratings and 
capacitor voltage ratings are those used 
for our prototype. Components with higher 
ratings may generally be used providing 
they are physically compatible. Com¬ 
ponents with lower ratings may also be 
used in some cases, providing the ratings 
are not exceeded. 


30 ELECTRONICS Australia, June, 1972 















own, actual size transparencies are 
available via the Information Service for 
50c. Quote the code number 72/ ps6. 

All but the power transformer and rec- 
tifiei assemblies are mounted on the front 
panel. As can be seen from the photographs, 
the IC heatsink, a piece of 18 gauge 
aluminium suitably shaped, is mounted on 
the front panel by the meter mounting 
screws on one side, and the potentiometer 
mounting bush the other side. The circuit 
board is mounted clear of the heatsink 
almost to the full length of the IC pins by 
6BA screws passing through each mounting 
flange hole of the IC, heatsink, and board, 
with suitable spacers or nuts on each screw. 
Once in position, the IC connections to the 
board are soldered. 

We have used a Ferguson PF3133 trans¬ 
former, a stock type which has a 30V 
centre-tapped secondary and a rating of 
500mA. With a full-wave rectifier using two 
BY 125 50 or similar diodes as shown, it 
delivers between 21 and 23 volts output for 
the regulator IC using the 2200uF reservoir 
capacitor. Other transformers may be used, 
providing they are capable of delivering 
500mA or more and have a voltage of not 
more than 20V RMS per side (ie, 40V CT). 

It would of course be possible to use a 
transformer with a single untapped second¬ 
ary, with a bridge rectifier circuit. Here 
again the transformer should have a rating 
of 500mA, or more, and a voltage of no more 
than 20V RMS. 

Although the MC1469R has provision for 
remote sensing, this facility would not 
really be in keeping with the concept of a 
simple general-purpose supply, and for this 
reason we have elected not to use it. We 
have brought the remote positive'sensing 
input of the IC out to a separate conductor 
on the wiring board, but this is simply 
linked across to the positive output. 

Those who would like to “gild the lily” 
could provide the remote sensing facility by 
bringing the IC sensing input out to a front 
panel terminal. This would normally be 
linked to the positive output terminal, and 
only disconnected when it is necessary to 
run a separate lead to the load to com¬ 
pensate for the voltage drop in long leads. 

But note that in order to achieve full 
remote sensing, it will also be necessary to 
isolate the IC heatsink from .the case of the 


The circuit diagram above shows 
how simple the design of a regulated 
variable supply becomes when the 
MCI469R IC is used. Note that pin 5 
of the IC may be used for remote 
sensing if required. 


At right is the supply opened to show 
the basic rectifier inside the case, 
and the way the printed board is 
supported by the IC and its heatsink 
bracket. 


supply, and bring the “negative” line on the 
wiring board out to its own front panel 
terminal separate from the negative output 
of the rectifier. Again the two negative 
terminals would be linked together nor¬ 
mally, and only separated to permit the 
negative IC line to be taken directly to the 
load toicompensate for losses in a long 
negative lead. 

Natually if this were done, the insulated 
IC heatsink would also allow the output of 
the supply to be “floated” with respect to 
earth. 

Components mounted on the wiring board 
should be wired close to the board, par¬ 
ticularly the smaller capacitors. Other 
connecting leads should be as long as 
necessary to make each connection com¬ 
fortable, but not excessively long. If these 
points are observed, no problems with in¬ 
stability or oscillation should be en¬ 
countered. 

The remaining sections of wiring can be 
readily assembled on tagstrips or 
tagpanels. These include the rectifier and 
filter system, mounted within the body of 
the case. The series meter multiplier 
resistors may be strung in series between 
the appropriate points, as shown in the 
photograph. 

If using the ATC case, place the power 



supply parts as close to and right across the 
back to provide sufficient clearance for the 
wiring mounted on the front panel. 

Well, there you have it. A very easily 
made little power supply, and one which 
will not cost nearly as much as a com¬ 
parable commercial unit. If carefully built, 
it should prove a real asset to any service 
shop or experimental bench. ® 


CLEARANCE SALE OF ELECTRONIC 
EQUIPMENTAND COMPONENTS 


Receivers, Transceivers Ex-Army & Citizens 
Band, Transmitters, Test Equipment, 
Oscilloscopes, Sig. Generators, Multimeters, 
Chassis Racks, Panels, Computer Parts & 
Boards, Power Transformers up to 6.6kV, 
Valves, Transistors, Potentiometers, etc., 
Speakers, Amplifiers. Cables — hook / up & 
Coaxial 50 & 70 Ohm; Multicore up to 50-Core. 
7,000 sq. ft. of Electronic Gear. Plenty of 
parking. Come and inspect. 

Open 10 a.m.-5 p.m. Weekdays, 9.30-12 
Saturday. 

SPECIAL THIS MONTH 

No. 62 Transceivers Army Type 1.6 to 10MHz: 
12-Volt operation. Price $39.50. 

50-Ohm coaxial cable %" diam. New 45c yd. 

WANTED TO BUY 

Receivers, Test Equipment, Ham Gear,Stereo 
Equip.: Top Prices Paid. 

HAM RADIO (DISPOSAL BRANCH) 

104 Highett Street, RICHMOND, VIC. 
Phone 42 8136 


ELECTRONICS Australia, June, 1972 


31 




















































MAGNETIC TAPE 

BULK ERASER 

Here’s a useful accessory for the tape recording enthusiast — a bulk eraser 
which will accept 5 inch and 7 inch spools of standard Vt inch magnetic 
recording tape. It can be built around two modified filter chokes or small 
power transformers, and operates from the AC mains. 



As every tape recordist knows, one of the 
best characteristics of magnetic tape over 
any other recording medium is its 
erasibility. 

Tape is erased by subjecting the magnetic 
material to an alternating or permanent 
magnetic field of sufficient strength to 
destroy any previous pattern. 

The permanent magnet method of 
erasure is the simplest, but is usually used 
only on the very cheapest recorders. 

The alternating field system uses a 
separate head, similar to the recording 
head, but with a much wider gap. While 
recording, this head is excited by a high 
frequency power oscillator at, typically, 40- 
lOOKHz. The oscillator power, about 1 watt, 
produces a flux of sufficient strength to 
erase any previous recording. The erase 
head is placed before the recording head in 
the direction of tape transport. 

Since recorders are already equiped with 
erase facilities, why use a bulk eraser? 

There are several reasons. In normal use, 
a tape will collect a whole range of items, 
many of them irelevant, personal, or even 
confidential. If, subsequently, the tape has 
to be passed into someone elses care, but 
only part of it contains relevant material, 
there is the problem of how to erase the 
remainder. 

While it can be done by simply running 
the tape through the machine in the record 
mode, with no signal input, this can be a 
tedious operation, particularly with a large 
reel of tape and a four track system. 

With a bulk eraser, the whole tape can be 



INDOOR-OUTDOOR STORAGE 

Seals out moisture—prevents 
corrosion—gives long or short term 
indoor-outdoor protection. 

EASY TO APPLY AND REMOVE 


Available from your accredited CRC Distributor 


by GEORGE HUGHES 




E O " p frame parallel connected 

Diagram showing either series (upper} or 
parallel dower) connections for the eraser 
coils. Dots denote abitrary ends of coils, 
either start or finish, assuming both coils 
are wound in the same direction. 


wiped clean in a few seconds before the vital 
recording is made. 

Again, there is a possible problem when 
tape is transferred from one machine to 
another. Unless the alignment of both sets 
of heads is the same it is quite possible that 
a recording made on machine No 1 may not 
be completely erased, for example, along 
one edge, when a new recording is made on 
machine No 2. If subsequently replayed on 
machine No 1, or a machine with similar 
alignment, a background of the old 
recording would appear behind the new one. 

Fairly obviously, bulk erasure, before 
transfering to machine No 2 would avoid 
any such problem. 

Finally, there is the problem of noise. 
While not usually a serious problem, there 
is little doubt that a tape which has been 
recorded and erased a number of times will 
have a marginally higher noise level than 
the first recording on a virgin tape, since 
there are many factors which will influence 


this, such as the grade of tape, the op¬ 
timisation of the bias level and frequency, 
etc, it is impossible to forecast just how 
serious the problem will be in any one 
situation. Suffice it to say that, where the 
very best results are required, bulk erase 
would seem to be good insurance. 

In essence, a bulk eraser is an AC electro¬ 
magnet whose field is strong enough to 
overcome any premagnetised pattern of 
oxide particles on a tape, and to leave them 
in such a random condition that the tape 
possesses no resemblance of a previous 
magnetic pattern. 

Commercial bulk erasers use a large 
multi-turn coil, usually connected to the 
50Hz mains, with provision to mount the 
reel of tape in close proximity to it and to 
rotate it. 

A good substitute for such a special coil is 
a pair of modified chokes or transformers. 
By adopting a “staggered” layout of the two 
windings it is possible to use relatively 
small units and still cover a 7in (177mm) 
reel of tape. 

A cheap bulk eraser can be made with two 
such windings, a few pieces of wood, some 
18 gauge aluminium, a press-button switch, 
a neon indicator, and a length of 3-core 
power flex and plug. 

Our eraser used a pair of CF396 Ferguson 
filter chokes, modified by removing the “I” 
section of the core. (See photo.) Whatever 
units are used, they will have to be modified 
to this configuration. / 

Removing the “I” section provides an 
»open magnetic circuit, allowing the 
magnetic field to pass through the tape in 
the final set-up. It also reduces the in¬ 
ductance and increases the current flow. 
While the increased current flow is 
desirable, there is a limit set by the ten¬ 
dency for the coils to overheat. Whatever 
units are finally chosen, their suitability, 
and the method of connecting them, will be 
determined by the heat generated during a 
typical duty cycle. 

Before spending money on new com¬ 
ponents, we suggest you “scrounge” for 
suitable windings, as components as large 
as are needed are not cheap when new. 
Windings extracted from TV vertical output 
transformers, small power transformers, 
vibrator transformers, etc, will be suitable 
with proper interconnection of their wind¬ 
ings. 

The core size should not be less than a lin 
(25mm) thick stack of lin “wasteless” 


32 ELECTRONICS Australia, June, 1972 






















lamination, in order to cover the full width 
of a 7in spool. 

(A “wasteless” transformer lamination is 
one where the winding spaces in the “E” 
equals the width of an “I”. The size of an 
“E” lamination refers to the tongue width, 
which is twice the width of the winding 
spaces. For a lin wasteless lamination, the 
width of the “I” will be 1 ^in, and its length 
will be 3 inches. Thus, a transformer 
lamination size can be gauged by its longest 
edge). 

Armed with the above information and a 
steel rule, it shouldn’t be hard to find two 
suitable items. Try to find two of the same 
type if possible. 

As a guide, windings with not less than 
about 2000" turns should be satisfactory. 
Small power transformers would probably 
have sufficient turns when all windings are 
connected in series. Assuming a design 
figure of 5 turns per volt, a 240V primary 
will have 1200 turns, and a 150V per side HT 
winding will yield a further 1500 turns. 
Total, 2700 turns. 

To correctly series-connect such win¬ 
dings, connect the primary to the ends of a 
length of power lead terminated in a 
suitable terminal block. Connect one end of 
the HT winding to one side of the primary, 
and the other end to a spare terminal to 
keep it away from other wires. 

Plug into a 240 volt outlet and switch on. 
Measure the AC voltage from the free HT 
terminal to the remaining 240 volt terminal. 
If correctly connected, the voltage right 
across the two windings should measure 240 
volts plus the HT nominal voltage. If less 



Detailed drawing of the lugs to be mounted 
either side of the slot. A variety of non- 
ferrous materials may be used. 



d»ck smith 
■lectronics 

CATALOGUE 


“At last! The real 
wholesale price of 
components revealed 
in my first 
catalogue 


HI-FI AMPS,I 

turntables! 

TAPE DECKS,! 
CASSETTES,] 
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than 240 volts, the HT winding connections 
should be reversed. Double check. 

When identified, the winding connections 
should be made permanent, with adequate 
insulation over the connections. 

With the connections established, the 
transformer core should be modified. 
Transformers are normally assembled with 
the “I” and “E” sections interleaved, as 
distinct from the separate “E” and “I” 
sections for a choke, with a strip of gap 
material between them. 

This means that the transformer core 
must be completely removed, the “I” 
sections discarded, and the “E” sections re¬ 
assembled all facing the one way. 
Removing the original core may not be 
easy. Varnished units will offer some 
resistance, but when one or t^wo laminations 



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ELECTRONICS Australia, June, 1972 33 
























have been removed, the remaining ones can 
be peeled off with the aid of a thin knife 
blade. Wax impregnated units are easier to 
work on. 

Place two mounting feet in position and 
clamp tightly with two through-bolts. Give 
the outer extremes of the laminations a 
squirt of lacquer to anchor them and 
minimise buzz. 

Assuming that the above requirements 
have been satisfied, it should be possible to 
connect the two windings in parallel and to 
the 240V supply without risk of serious 
overheating during the brief period they 
will be on. If it should transpire that the best 
available units have insufficient turns, and 
do tend to overheat, they may be connected 
in series. They should be identical units for 
this arrangement. 

We housed the complete eraser in a 
simple box made from plywood and 
aluminium. The base and two ends of the 
box are of plywood, and the front, rear, and 
top is folded from one piece of aluminium. 

The wooden portion is made from a 3 
5/ 8in (93mm) wide strip of plywood (or 
Pineboard). The base is 5V 2 in (140mm) long 
and the two ends are 4in (102mm) high. One 
corner of each end is cut off, lin in each 
direction to form an angle of 45°. 

Fasten the end pieces to the base (on the 
end grain) with PVA wood glue and a few 
thin nails. When the glue has set, sand the 
whole assembly. Finish may be to your own 
taste. We applied a coat of full gloss paint 
and adhesive backed wood-grained plastic 
sheet, such as “Con-Tact”. 

The aluminium cover has a central slot 
through which the tape spool is inserted. On 
each side of the slot is a lug shaped as shown 
in the accompanying drawing. The two slots 
are designed to support a simple axle, such 
as a pencil, which, in turn, supports the reel. 
One pair of slots suits a 5in (127mm) reel 
and the other a 7in reel. The lugs may be 
made from any non-magnetic material. We 
used a piece of V^in (6.5mm) acrylic, but 
wood, aluminium, brass etc, could be used 
by slightly modifying the design. 

The cover is best marked out, drilled, and 
slotted in the flat. Then bend to shape and 
rub the outer surface with a fine (500) grit 
“wet and dry” paper, using a rubbing block 
and plenty of water. Finally, spray with a 
clear enamel. 

Mount the first coil as far forward as 
possible without it fouling the cover when in 
place. Place it so that the open end of the 
laminations are not less than 5 / 16in (8mm) 
to the RHS of a centerline drawn across the 


The internal layout 
of the bulk eraser. 
Note particularly 
how the two coils 
are offset from each 
other. This provides 
adequate coverage 
for the larger reels. 
The folded card¬ 
board between the 
coils is to protect the 
open ends of the 
windings. Since the 
unit will be con¬ 
nected to the mains, 
make sure all wiring 
is adequately in¬ 
sulated. Note the 
damp on the mains 
lead. 


depth of the base. Use countersunk machine 
screws (Vein Whit or 4BA) and nuts, in¬ 
serted from the underside. 

To the LHS of the centerline, and at the 
same distance from it as the first coil, 
mount the second coil with its front edge 
level with the re&r edge of the first coil. 
Cover the underside of the base with Vain 
felt cemented with a suitable contact 
adhesive. 

To protect the open ends of the windings, 
cut a piece of thin cardboard 3V2in x 7V2in 
(89mm x 190mm) and form it into a “U” 
shape which will fit between the two core 
assemblies. Leave room in the rear section 
for interconnecting cables. Fasten with 
contact adhesive. 

Before connecting the windings, ascertain 
arbitrary ends, ie, “start” and “finish,” of 
each one. Code lead-outs from each winding 
suitably — either by knots or colors. The 
two methods of connection are shown in the 


ut 


so 


on 


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34 ELECTRONICS Australia, June, 1972 


accompanying diagram. 

Fit the neon indicator, fuse holder, press 
button switch and mains lead (by a clip) to 
the aluminium cover. Connect to the ap¬ 
propriate leads as shown in the diagram. 

With care, lower the aluminium cover 
over the assembly, making sure all leads 
are tucked in the space available to prevent 
them being pinched as the cover is screwed 
down. 

To use the eraser, first take two 
precautions. Remove all valuable tape 
recordings to a distance of at least 3ft (1 
metre) from the eraser, otherwise there 
may be a risk of partial erasure. Secondly, 
remove your watch. Even if anti-magnetic, 
it may not take kindly to having the hair¬ 
spring rattled at 50Hz! 

Place the tape spool in position with a 
pencil as an axle. Five inch spools use the 
inner slot and 7 inch spools the outer one. 

Press the power button and rotate the 
spool at least twice very slowly without 
releasing the button. Application of power 
will be accompanied by a heavy hum. 

If you release thr button momentarily, 
count your rotation of the spool from the 
time and position you released the button. If 
power is disconnected with the spool in 
position, a “thump” will be recorded for 
every revolution of the tape. 

After rotation, and still with power ap¬ 
plied, slowly withdraw the spool a full arm’s 
length from the eraser, and then release the 
button. 


If the spool is rotated or withdrawn from 
the eraser too quickly, a burble will be 
recorded for every revolution of the spool. 

Use the eraser only for sufficient time to 
erase a tape, as excessive “on” time may 
cause the coils to overheat, with the risk of a 
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ELECTRONICS Australia, June, 1972 


35 

























































Sync & Pattern 
Generator for TV 


Construction details for the new instrument, whose operation was 
described last month. Build it for CCTV or to prepare for colour TV! 


Second of two articles by JAMIESON ROWE 


The generator described in these articles 
is a flexible instrument which produces two 
different types of television signals. It 
produces a variety of test pattern signals, 
which among other things can be used for 
such purposes as convergence testing and 
adjustment of colour TV receivers, and 
linearity adjustment of monochrome 
receivers. 

In addition it also produces a complete set 
of horizontal sync and blanking pulses, and 
is thus suitable for such purposes as inter¬ 
locking closed-circuit television (CCTV) 
cameras, or serving as the master sync and 
blanking generator for an amateur televi¬ 
sion (ATV) station. 

All of the signals generated by the unit 
conform substantially to the Australian TV 
standards, ie, they have a 625-line 50-field 
raster with a locked 2:1 interlace, and 
shaped sync and blanking pulses which are 
completely adequate for CCTV and ATV 
use. The test patterns can be displayed by 
any normal receiver or monitor designed 
for Australian broadcast television signals. 

In the first article, published last month, I 
discussed the performance of the unit, and 
described the basic operation of each of its 
functional circuit sections. This article will 
complete the story by describing how to 
construct the generator. 



The circuit of the complete generator is 
shown opposite. This may seem a little 
bewildering, but if you followed the break¬ 
down of its operation given last month, it 
should not be hard to identify the various 
sections and trace the flow of signals. Refer 
back to the diagrams given in the first 
article if your memory needs a little 
refreshing. 

As may be seen the 3.125MHz master 
crystal oscillator is a straightforward 
circuit using a Motorola MC799P dual buffer 
IC. I have used this oscillator configuration 
on previous occasions, such as the Crystal 
Frequency Calibrator of September 1969 
and the 70MHz Digital Frequency Meter of 
May-June 1970. It gives reliable and stable 
operation with a minimum of components, 
even though in this case the frequency of 
operation is near the rated maximum 
frequency for the RTL devices. 

A small ceramic trimmer is provided in 
the oscillator circuit to permit fine adjust¬ 
ment of frequency. This allows the line and 
field scanning frequencies produced by the 
SPG to be set to their correct values by 
comparison with a suitable reference such 
as the signals radiated by an ABCTV station 
during a national live program. Naturally 
the stability of the SPG signals will not be as 
good as such a reference, but with a 



These shots show the inside of the case and 
the rear of the new sync and pattern 
generator. The row of sockets on the rear 
would only be required if the unit is to be 
used as a sync generator; they could be 
omitted if it is only to be used as a pattern 
generator for servicing work. 


ELECTRONICS Australia, June, 1972 


stability of about 1 part in 100,000 provided 
by the crystal, it is sufficient to justify the 
vernier adjustment. 

All of the stages in the main frequency 
divider chain of the unit use Motorola 
MC790P dual J-K flip-flop ICs. Because 
minimum-device logic configurations are 
used, a total of only ten of these devices are 
required. A single Fairchild FuL923 J-K 
flip-flop is used for the x2 horizontal fre¬ 
quency divider. 

Most of the gating required for the syn¬ 
thesis of horizontal and vertical blanking 
and sync pulses is performed using 
Motorola MC724P quad 2-input gates, of 
which four are used. For the final gating 
and buffers used to produce the various 
logic outputs, Motorola MC788P dual 3-input 
buffers are used, three in all. 

At this stage you may well be asking 
yourself why I have used simple RTL 
devices for the basic logic circuitry of the 
generator, when nowadays the higher per¬ 
formance TTL devices are readily available 
at approximately the same cost. Some 
readers may even be inclined to dismiss the 
design as “dated” because it uses the now 
less fashionable RTL devices. 

My reason for using the RTL devices is 
that they are quite capable of doing the job 
required here, while at the same time they 
are not nearly as critical as the higher- 
performance TTL devices in terms of 
layout, bypassing, and so on. Where the 
higher performance is not really required I 
believe it would be unwise to use TTL 
devices and thus needlessly increase the 
likelihood of readers getting into strife. 

All of the components and wiring 
described this far are mounted on a printed 
wiring board, which measures 6-7 / 8in x 
4 3 /4in (175 x 121mm). This board therefore 
carries most of the wiring of the SPG, and 
simplifies construction considerably. The 
diagram of Fig. 7 shows the way in which 
the board is wired. 

The oscillator trimmer capacitor for 
which the board pattern has been designed 
is the same 2-8pF NPO ceramic unit used in 
previous projects, the type DV11PR8A 
distributed by the Imported Components 
Division of Plessey Ducon Pty Ltd. 

The only sections of the circuit not 
mounted on the wiring board are the video 
test signal synthesiser section and the 
power supply. 


36 





















ELECTRONICS Australia, June, 1972 


37 






























































































































































































































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The video test signal section was 
described in some detail in the first article. 
It uses a Fairchild FuL914 dual 2-input gate 
IC to invert the horizontal and vertical sync 
pulses, and then discrete circuitry to syn¬ 
thesise the video waveform. The discrete 
circuit uses three general-purpose NPN 
silicon transistors such as the 2N3565 or 
BC108, together with a silicon PNP tran¬ 
sistor such as the 2N3836A or TT608. 

The components and wiring of the video 
section are mounted on a 12-lug section of 
miniature resistor panel, whose wiring is 
shown in Fig 8. 

The power supply of the generator is a 
straightforward circuit using a transformer 
and full-wave rectifier followed by a series 
regulator using a zener diode reference. 
The supply is designed to deliver a nominal 

3.7 volts at approximately 690 milliamps, 
with low ripple. 

Silicon rectifier diodes such as the 
BY126 / 50, EM401 or similar may be used 
for the power supply rectifier, while the 
series regulator may be any suitable NPN 
medium power TO-66 device such as the 
Fairchild AY8170 or AY8171, the 2N3054, the 
RCA type 40250, or even the germanium 
AD 161. The zener diode should be any type 
with a nominal voltage around 4.3V and a 
rating of around 400mW. I used the Philips 
BZY88 / C4V3, but other types may be used 
if on hand. 

If the diode used has a breakdown voltage 
much lower than 4.3 volts, it may be 
necessary to wire one or more forward- 
biased silicon diodes (the rating is not 
important) in series with it to bring the 
supply output voltage up to between 3.6 and 

3.8 volts. Each diode added in this way will 


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Response . 30-7,000Hz 

Capacitance . 800 picofarads 

Ideal Load . 5 megohms 


effectively increase the zener voltage by 
about 0.6V, and the output voltage by a 
slightly smaller amount. 

Actually if a 4.3V or lower zener is 
completely unobtainable, it is quite in order 
to use a string of low cost forward-biased 
silicon diodes in series to build up the 
required voltage. Seven or eight diodes 
would be required. 

The components and wiring of the power 
supply are supported on another section of 


Fig. 7 

miniature resistor panel, in this case a 
section 8 lugs long. The wiring of this panel 
is shown in Fig. 9. 

From the photographs it may be seen that 
the prototype generator is housed in a 
standard small instrument case, measuring 
7Vfein x 5in x 4in (190 x 130 x 105mm). This 
case was used mainly because I had it on 
hand. If you intend building the unit for use 
with CCTV cameras or for ATV work, this 
physical format should be quite ap¬ 
propriate. 

On the other hand if you mainly intend 
using it for convergence work with colour 
TV sets and monitors, and for linearity 
work with monochrome sets, then a simpler 
format and a more compact case could be 
used. The sync and blanking output con¬ 
nectors could be left off if not desired, and 
the wiring to them from the board ignored. 
Similarly the CRO sync signal switch and 
output connector could also be left off if not 
required. 

On the prototype generator the front 
panel provides the mains switch and pilot, 
the test pattern selector switch, the CRO 
sync switch and the output connectors for 
the video test pattern and CRO sync signals. 
The vertical and horizontal sync and blank¬ 
ing outputs and the composite blanking 
output connectors are mounted in a vertical 
row on the rear of the case, as shown in the 
photograph. The printed board is attached 
to the rear of the front panel by means of 
four 1 Vfein long Vain Whitworth screws, using 
three nuts on each screw to space the board 
from the panel by lV 4 in. 

The power transformer and power supply 
wiring strip are mounted on the bottom of 
the case, with the series regulator transis¬ 
tor mounted externally on the centre of the 
case rear. The wiring strip for the video test 
signal circuitry is mounted on the case rear 
above the regulator transistor. 

As most of the involved wiring of the 
generator is performed by the printed wir¬ 
ing board, construction of the unit is quite 
straightforward. Using the diagrams and 
photographs it shbuld not present any 
problems, even for the constructor as yet 
unfamiliar with ICs. 

Before closing there are a few comments 


6,Sla 


H. SYNC 


ROTOR Sib 
Sla 

(TS) 
SIGNAL 
GATING 

COMPOSITE 

BLANKING 


-f 3.7V 


V. SYNC 

V. BLANK 


PI. 3. Sla P 4 . 


P6Slb 


38 ELECTRONICS Australia, June, 1972 




































TS 


+ 3.7V 


Fig. 8 



VS HS 



which I should perhaps make. The first 
concerns the horizontal lines test pattern; 
as you may have noticed from the 
photographs given last month, this pattern 
does not have the lines equally spaced. 

It would of course have been very desir¬ 
able to have the lines of the pattern equally 
spaced, as this would simplify considerably 
the use of the pattern in checking and ad¬ 
justing vertical scan linearity. However try 
as I did when developing the generator, I 
couldn’t find any easy way of generating a 
pattern with a reasonable number of 
equally spaced horizontal lines. The pulses 
and frequencies are just not readily avail¬ 
able from the divider chain and logic cir¬ 
cuits, hence the pattern shown. 

Actually despite first appearances, the 
pattern produced is still very useful for 
vertical linearity work. After a bit of 
practice it is really quite easy to mentally 
and visually allow for the alternate 1 line / 2 
lines spacing, and adjust the vertical scan 
linearity to make the pattern “uniformly 
alternating”. 

My next comment concerns the pattern in 
which the vertical bar is modulated with the 
1.562MHz test frequency. Because the 
1.562MHz signal used for this pattern is 
derived directly from a flip-flop in the 
divider chain, its peak-to-peak amplitude is 
less than the 3V available from the output of 
a logic gate. Hence the bar modulation for 
this pattern tends to be a little lower than 
with the other patterns. 

This need not cause problems, as the 
contrast control of the set or monitor can 
usually be turned up to compensate. For 
this reason I have not added additional 
components or wiring in order to overcome 
the effect. However if you find it irritating 
or it prevents serious evaluation of high- 
frequency response, I can suggest two ways 
in which it might be remedied. 

One way would be to arrange that the gate 
in IC14 used to buffer and shape the 



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40 ELECTRONICS Australia, June, 1972 


AD45 




















+3.7V 



3.125MHz signal is also used to perform the 
same functions for the 1.562MHz signal. 
This would involve using a three-pole 6-posi¬ 
tion switch for Si, with the third pole used to 
select the signal fed to the gate input. The 
copper conductor on the board linking the 
gate input to the 3.125MHz crystal oscillator 
would have to be carefully cut with a razor 
blade, and wires taken to the switch from 
both sides of the cut along with the wire 
from the 1.562MHz output. The output of the 
gate would then be connected to position 5 of 
Sib, as well as position 6. 

The other way, and probably the simpler, 
would be to add a simple one-transistor 
buffer and shaper in the line between the 
1.562MHz board output and position 5 of Sib. 
This would involve nothing more than a 
2N3565, BC108 or similar NPN silicon 
transistor, with an 820 ohm resistor to 
+3.7V in the collector circuit, and a 2.2K 
resistor in series with the base, possibly 
with an OA91 diode in parallel to speed up 
turnoff. Fig. 10 shows the idea. 

My final comment concerns the 
possibility of providing a cross-hatch 
pattern test signal, if this is required. 
Although a cross-hatch pattern offers little 
that is not provided by the vertical lines, 
horizontal lines and dot patterns, there may 
be some constructors who would like to 
have such a pattern available. Needless to 
say, it is possible to produce such a pattern 
in the present generator, because we have 


the necessary vertical and horizontal line 
signals available, and a cross hatch signal 
is formed from these. But whereas the dot 
pattern is formed by a logic AND operation 
combining the two, the cross-hatch is for¬ 
med by an OR operation. 

The simplest way of producing a cross- 
hatch logic signal with this generator is 
shown in Fig. 11. A Fairchild FuL914 dual 
gate IC is all that is required, with one gate 
wired as an inverter for the 312.5kHz ver¬ 
tical lines signal and the other used to 
combine this signal with an inverted 
horizontal lines signal taken from pin 2 or 
pin 5 of IC16 on the main wiring board. 

The output from the circuit would be fed 
to a suitable position on switch Sla or Sib — 


V. LINES 
(312.5kHz) 


H. LINES 
FROM 5 OR 2 
OF IC16 


FuL914 

1-1 



Fig. 11 


replacing one of the patterns at present 
provided. Which pattern is omitted in 
preference to the cross-hatch is a decision I 
will leave up to you. It would also be 
possible to keep all the present patterns as 
well as the cross-hatch, by using a 7-position 
switch, but bear in mind that a two-wafer 
switch may involve space problems. 
Whichever section of Si the cross-hatch 
signal is taken to, the corresponding lug on 
the other section should be earthed. 

That I think ends the story. It would 
perhaps have been nice to have been able to 
describe the use of the generator for con¬ 
vergence adjustment of colour TV sets, but 
space will not permit. We will deal with this 
subject later, in the detail it deserves. ® 


Parts needed for Sync Generator 


1 Instrument case, 7'A in x 5in x 4in. 

1 Printed wiring board, 72/ c2. 

1 Power transformer, 240V to 12.6V CT 
at 1A. 

1 Rotary switch, 2-pole 6-position. 

1 Quartz crystal, 3.125MHz. 

2 Miniature toggle switches, SPST. 

7 Co-axial connectors. 

1 Miniature pilot bezel, 6V 50mA. 

SEMICONDUCTORS 
10 MC790P dual J-K flip-flop 
4 MC724P quad 2-input gate 

3 MC788P dual 3-input buffer 
1 MC799P dual inverter-buffer 
1 FuL923 J-K flip-flop 

1 FuL914 dual 2-input gate 
3 2N706, 2N3565, BC108, etc 
1 2N3638, TT3638, TT608, etc 

1 2N3054, AY8170, AD161 or similar 

2 OA91 or similar 

2 BY126/ 50, EM4005 or similar. 

1 BZY88/ C4V3 or similar 

CAPACITORS 
1 39pF NPO ceramic 

1 .001 uF 100V polyester 

2 .0047uF 100V polyester 
2 .047uF 100V polyester 
2 0. luF 100V polyester 


1 IOOuF 6VW electrolytic 
1 IOOOuF 6VW electrolytic 
1 2200uF 10VW electrolytic 
1 2-8pF variable ceramic, NPO 

RESISTORS 

Half-watt, 5% tolerance: 3 x 18 ohms, 2 
x 22 ohms, 2 x 100 ohms, 4 x 470 ohms, 1 
x 560 ohms. 

MISCELLANEOUS 

12-lug and 8-lug sections of miniature 
resistor panel; socket for quartz crystal; 
4-segment section of "B-B" mains 
connector strip; control knob for 
selector switch; mains cord and plug, 
also C-clamp for cord; handle for case, 
also rubber feet; 4 x I 1 /in screws for 
mounting printed wiring board; nuts, 
screws, solder lugs, connecting wire, 
etc. 

NOTE: Resistor wattage ratings and 
capacitor voltage ratings are those used 
for our prototype. Components with 
higher ratings may generally be used 
providing they are physically compatible. 
Components with lower ratings may 
also be used in some cases, providing 
the ratings are not exceeded. 



Ceramic 

Capacitors 


SPECIALISTS IN 

■ Disc Ceramics 

■ Barrier Layer 

■ Hi-K, Hi-Voltage 

■ Temp. Compensating 

See the Specialists in Components and Service 


Hawker Siddeley 
Electronics 


SYDNEY 93 0221, MELBOURNE 387 1899, 
BRISBANE 47 4311, ADELAIDE 46 5941, 
_PERTH 71 8766. 




T. & M. ELECTRONICS 


P.O. Box 57, HABERFIELD 2045 


AC125 

65C 

2 N 2926 

65c 

AC126 

65C 

2 N 3053 

1.00 

AC127 

80c 

2N3054 

1.50 

AC127 / 128 

1.50 

2 N 3055 

1.60 

AC 128 

70C 

mat. pr 

3.40 

AC187 

90c 

2 N 3638 

50c 

AC187 / 188 

1.70 

2 N 3638a 

60C 

AC188 

80c 

2N5459 

95C 

ADI 49 

1.80 

2N5485 

1.40 

AD161 / 162 

2.70 

2 N 6027 


BC107 

55C 

(D13T1) 

1.20 

BC108 

35C 

40250 

1.90 

BC109 

40c 

40408 

2.25 

BC177 

65c 

40409 

3.00 

BC178 

60c 

40410 

3.00 

BC179 

65c 

DIODES 


BD139 

2.40 

BA102 

85c 

BD139.140 

5.00 

OA90 

13C 

BF115 

60c 

OA91 

15c 

BF167 

80C 

OA95 

25c 

BF177 

1.20 

OA202 

40C 

BFY50 

95c 

IN 4004 

35C 

BRY39 

1.40 

IN 4007 


D13T1 

1.20 

(lamp lOOOv) 
BYZ 13 

80c 

MPF105 

95c 


OC26 

1.90 

(6amp 200v) 

60c 

OC28 

2.20 

SILICON BRIDGES 

OC29 

2.30 

1A 100V 

1.10 

OC35 

2.20 

1A 400V 

1.60 

OC36 

2.30 

2A 200V 

1.70 

OC44 

40c 

ZENERS 


OC45 

OC71 

OC72 

OC74 

OC81 

40c 

40C 

40C 

60c 

55c 

all voltages 
3.3 to 33V. 
BZY 08 type 

1.5W type 

55c 

1.00 

0071 

60C 

SCRs 


0CP71 

2.40 

15A 100V 

2.00 

TAA300 

2.85 

15A 400V 

3.00 

2 N 706a 

60C 

(Suit speed control, 

2N2646 

1.30 

etc) 


Post 15c 

(SORRY NO C.O.D.) 



RETURN MAIL SERVICE 


SEMI-CONDUCTOR SPECIALISTS 


ELECTRONICS Australia, June, 1972 


41 






























PA amplifier/mixer 


Do you have the need for a compact but flexible public-address amplifier? If 
you have a few hours to spare you can build this new 20 watt solid-state 
unit — it has two microphone channels and two ceramic cartridge channels, 
with full mixing facilities. 

an audio project by LEO SIMPSON 


For a unit that is so compact, measuring 
10 x 10 x 4 inches (254 x 254 x 102mm) in¬ 
cluding knobs and feet, this new 
Playmaster public address amplifier offers 
great flexibility, and it has high quality 
specifications to match. Although not high- 
powered, it will deliver 21 watts continuous 
power into an 8-ohm load or 13 watts con¬ 
tinuous into a 16 ohm load — adequate for 
most ordinary PA applications. 

Harmonic distortion at 1kHz for 21 watts 
output is less than 0.3 f c, while at lower 
powers it is typically less than O.p;. Power 
bandwidth using 3dB points and a rated 
distortion of 0.5^0 is from 20Hz to 20kHz. 

There are two microphone inputs, with 
individual level controls designated Mic 1 
and Mic 2. With an input impedance of 100k 
and a sensitivity of better than 5mV for 21 
watts into 8 ohms, the inputs are suitable for 
medium to high impedance dynamic 
microphones. 

There are two phono inputs, again with 
their own individual level controls. These 
have a sensitivity of 250mV and an input 
impedance of 500k, making them suitable 
for medium to high output ceramic or 
crystal cartridges. The input impedance of 
500k is not optimum for piezoelectric car¬ 
tridges but the slight reduction in bass 
response is not a problem for public address 
work In fact the reduction becomes 
negligible if a stereo cartridge is used, with 
both channels connected in parallel — this 
increases the source capacitance and thus 
reduces the required input impedance for 
good bass response. 


But note that low output ceramic car¬ 
tridges such as the Decca Deram or Con¬ 
noisseur SCU-1 are not suitable for use with 
this amplifier. 

A simple “top-cut” tone control is fitted 
and this acts on all input signals. Maximum 
available treble attenuation is -l6dB at 
10kHz. This is more than adequate to take 
care of scratchy records and peaky 
microphones. 

Interaction between the various input 
level controls is negligible at less than ldB 
over the audible frequency range. 
Frequency response for both microphone 
and phono inputs is + ldB from 20Hz to 
20kHz. 

Signal -to-noise ratios range from -60dB 
for phono inputs to -48dB for microphone 
inputs. These figures are with respect to 21 
watts into 8 ohms, are unweighted (ie, 
wideband noise) and are taken with inputs 
open-circuit. The figures improve con¬ 
siderably when the inputs are loaded. With 
level controls set for normal use, the am¬ 
plifier is very quiet. 

Extensive precautions have been taken to 
ensure freedom from RF breakthrough 
from such sources as taxis, radar, broad¬ 
cast and shortwave stations. The amplifier 
is also insensitive to mains-borne in¬ 
terference such as commutator hash from 
universal motors, clicks and pops from 
switching inductive loads. 

Electronic short-circuit protection 
facilities have not been provided, as fuse 
protection has been found to be quite 
adequate. However the amplifier should not 


Power: 21 watts continuous into an 8-ohm 
load: 13 watts continuous into a 16 ohm 
load. 

Distortion: Less than 0.3 at 21 watts 
into 8-ohms at 1kHz; at lower power 
within range 100Hz to 10kHz, typically 
less than 0.2 for microphone and phono 
inputs. 

Frequency response at 1 watt: ± ldB from 
20Hz to 20kHz for microphone and phono 
inputs. 

Tone control: O - 16dB cut at 10kHz. 
Inputs: Unbalanced microphone inputs 
with sensitivity better than 5mV for 21 
watts at 100k input impedance; Phono 
inputs 250mV at 500k. 

Signal-to-noise ratio: better than 60dB for 
phono inputs; better than 48dB for 
microphone inputs. 

Control interaction: less than ldB over 
audible range. 


be used with loudspeaker loads lower than 8 
ohms, to ensure completely reliable 
operation. 

Under normal conditions and when used 
for public address, the amplifier will run 
cool or just slightly warm to the touch. If it 
becomes very hot at the rear of the chassis, 
it is either being overdriven (which should 
be painfully audible), or is not getting 
sufficient ventilation, or for some reason is 
unstable at radio frequencies. In all these 
cases, corrective action should be taken 
immediately to prevent damage occurring. 

The heart of the unit is a new power IC 
device, the TA 20B. This is a 20 watt thick 
film hybrid IC distributed in Australia by 
STC. The internal circuit is shown in Fig 1. 
The amplifier circuit is based on the con¬ 
ventional “quasi-complementary” class-B 
configuation but has several interesting 
features. 

A differential amplifier stage consisting 
of Trl and Tr2 establishes the amplifier DC 



FIG. 1. COMPACT20 WATTS. The new integrated circuit 
AFpower amplifier is shown approximately actual size. An 
equivalent circuit of the thick film hybrid IC is shown at 
the right. 


m 



42 ELECTRONICS Australia, June, 1972 












































... features new power 1C 



“half-supply” voltage across the output 
coupling capacitor, making it relatively 
independent of supply voltage fluctuations. 
This assures symmetrical clipping when 
overload occurs. The main negative 
feedback loop, which applies both AC and 
DC feedback, is from pin 2 to the base of Tr2 
via a resistor. 

Tr3 provides further voltage am¬ 
plification for the input signals and acts as a 
class-A driver stage for the output driver 
transistors Tr6 and Tr7. Phase-splitting for 
the output NPN transistors takes place in 
the driver transistors. 

The diode in series with the emitter of Tr7 
improves the symmetry of the quasi¬ 
complementary output stage and greatly 
reduces the harmonic distortion at low 
power levels. 

The quiescent current for the output stage 
is set by the voltage drop across the 
Darlington transistor pair consisting of Tr4 
and Tr5. There is no means of adjusting this 
current externally. Normally it should be in 
the region of 30mA and no more than 50mA. 

Boot-strapping (ie, positive feedback) is 
intended to be applied via a 47uF 25VW 
capacitor from the output at pin 2 to the 


input of Tr6 at pin 4. This ensures tnat the 
full voltage swing is available at the output. 

Typical voltage gain of the power am¬ 
plifier is 30 times for all load impedances. 
This results in a basic sensitivity of better 
than 450mV for 21 watts into 8 ohms. Input 
impedance is 20k minimum. 

For the basic power amplifier there are 
eleven external components, beside the 
2200uF output capacitor, associated with 
the TA-20B amplifier. These are mounted on 
a printed board measuring 4 x 3‘ 4 inches. 
Besides the 47uF bootstrap capacitor 
mentioned above, there are two supply 
decoupling capacitors, 47uF and 250uF and 
an RF supply bypass capacitor, O.luF. The 
last mentioned capacitor is mounted on the 
underside of the board, directly between 
pins 1 and 3 of the TA 20B. 

In addition, there is the external part of 
the feedback network, consisting of lk and 
47uF 25VW capacitor in series. The lk 
resistor sets the overall gain while the 47uF 
capacitor sets the low frequency roll-off 
point. The rest of the components on the 
board are the 0.33uF input coupling 
capacitor, a Zobel output damping network 
consisting of a 4.7 ohm resistor and .047uF 


capacitor in series, and also an RF choke LI 
in parallel with a 10 ohm resistor. 

These four last-mentioned components 
ensure that the amplifier is stable with 
highly reactive loads, both inductive and 
capacitive. Thus the amplifier is completely 
stable with any capacitance up to luF 
shunting the load. 

Driving the power amplifier is a four- 
channel mixer. It has two microphone 
preamplifiers, two impedance-matching 
stages for the phono inputs, passive mixing 
and a voltage amplifer stage to make up the 
losses in the mixing circuitry. 

The microphone preamplifiers are direct- 
coupled NPN transistor pairs with several 
interesting features. Bias for the input 
transistor is derived from the junction of the 
270 and 560 ohm resistors in the emitter 
circuit of the second transistor. This circuit 
assures DC stability of the output voltage at 
the collector of the second transistor. AC 
negative feedback is applied from the 
collector of the second transistor to the 
emitter of the first transistor via the 100k 
resistor shunted by a 47pF capacitor. The 
capacitor rolls off the response above the 
audible range to assure low RF sensitivity. 

In addition to rolling off the response at 
high frequencies, there is an RF at¬ 
tenuation network in the input cir¬ 
cuit. It consists of a series 10k resistor 
and shunting lOOpF capacitor. This 
prevents strong RF signals entering the 
base of the first transistor, which due to its 
basic non-linearities can “detect” RF 
signals and thus make them audible. 
Voltage gain of each preamplifier is ap¬ 
proximately 50 times. 

The impedance matching stages for the 
phono inputs are identical, each being an 
emitter-follower using an NPN transistor. 
Voltage gain of these stages is 0.9. 

Output signals from each of the pream¬ 
plifiers and impedance matching stages are 

Turn page for circuit diagram 









GRFATFST RANfiF l,,ustrated ( ,eft to r| 9 ht ) 

URLMILOI io watt, 10 watt mini, 20 watt 

Only MICO gives you a complete range of 12 models 
from the extra lightweight mini to the 70 watt heavy duty 
model. Voltage range includes 4,6,12,24,32 & 50 V. 


OTHER FEATURES INCLUDE I longer bi? life 

• repairable • precision made • guaranteed • Australian 
made • exclusive variable voltage transformers available. 


Manufactured, sold & serviced by 

WATKIN WYNNE PTY. LTD. 

32 Falcon Street Crows Nest 2065 NSW Australia 

Detailed literature available 


MINIATURE 

SOLDERING 

IRON YOU 
DONTHAVE 
TO SWITCH 
ON&OFF! 

Yes MICO gives you the outstanding advantage of 
^ constant heat soldering, you don't have the worries 
^ of heat control. Overheated soldered joins can 
crystallise, under-heated give a dry joint. MICO 
stays at around 500° F - the ideal temperature. 


OBTAINABLE THROUGH TRADE HOUSES EVERYWHERE 


PA amplifier, cont 


fed to a voltage-amplifier stage consisting 
of an NPN transistor. Since this stage has 
an input impedance of 10k, the voltage 
losses in the mixing network are 5:1. 
Overall voltage gain of the following stage 
is approximately 10 times, which therefore 
more than compensates for the loss. 

Again, the response of this stage is rolled 
off above the audible limit to reduce RF 
sensitivity. This is accomplished by the 
lOOpF capacitor connected from base to 
collector. 

Current drain of each of the microphone 
preamplifiers is 4 milliamps, the emitter- 
followers 0.8 milliamps and the mixer 
voltage-amplifier 1.2 milliamps. All of the 
circuitry just mentioned is accommodated 
on a printed board 3x8 inches. With two of 
these printed boards a high performance 
stereo mixer can be easily assembled. 

The power supply for the amplifier is 
simplicity itself. The power transformer 
has two 32 volt windings which are con¬ 
nected in series to give 64 volts centre- 
tapped. The power transformer is the same 
as for the 10-plus-10 stereo amplifier 
published in April 1969; suitable type 
numbers are the Ferguson PF 2876 or the A 
& R PT 6413. A full-wave rectifier consisting 
of two 200 PIV / 1 amp silicon diodes sup¬ 
plies the 2200uF filter / reservoir capacitor. 

A 1-amp fuse connected in series with the 
centre-tap connection provides protection 
for the amplifier and power supply compo¬ 
nents against short circuit loads and over 
loading. 


TO TRANS SEC. CT - 2200uF FILTER 

VIA 1A FUSE CAPACITOR 



MIXER BOARD 


POWER SUPPLY DIODES are mounted on 
tagstrip as shown above. Right hand earth 
lug is the only chassis connection to power 
amplifier. 


CONSTRUCTION: The amplifier is 
assembled in a chassis with overall dimen¬ 
sions of lOVs x 3V4 x 8% inches (257 x 83 x 
213mm). The chassis is, in fact, a slightly 
modified version of that used for the 
Playmaster 129 integrated circuit amplifier 
published in October 1970. It was supplied 
by courtesy of Heating Systems Pty Ltd, 19- 
21 The Boulevarde, Caringbah, 2229. We 
assume that chassis will be available for the 
PA amplifer shortly after this issue goes on 
sale. 

First components to be mounted are the 
2200uF/50VW can-type electrolytic 
capacitors. The fuseholder, power trans¬ 
former and input sockets can then be in¬ 
stalled. Note that the “button-type” micro¬ 
phone sockets must be insulated from the 
chassis using the rubber washers provided. 
The “earthy” sides of the sockets are 
connected to an adjacent tagstrip on the 


44 


ELECTRONICS Australia, June, 1972 










































df) 


ELECTRONICS Australia, June, 1972 


45 


20W PUBLIC ADDRESS AMPLIFIER 











































































































































New Extended Range 


New Low Prices 


New Miniaturization 


0 


HYBRID 
AMPLIFIERS 
3 to 50 WATTS 


INTEGRATED 

SOUND 

POWER 


Branches and Distributors: 

Sydney: Moorebank Ave., Liverpool, 
2170. Phone: 602-0333. 

Sydney: Geo. Brown & Co. Pty. Ltd., 
Cnr. Sussex & Druitt Sts., Sydney. 
2000. Phone: 29-7031 
Melbourne: 314 St. Georges Road, 
Thornbury. 3071. Phone: 480-1255. 
Melbourne: Radio Parts Pty. Ltd., 
562 Spencer St., Nth. Melbourne. 
Phone: 329-7888. 

Canberra: 90 Wentworth Avenue, 
Kingston. 2604. 

Telephone: 95-9883. 


CONTACTyourSTC 

REPRESENTATIVE 

Tasmania: W. & G. Genders Pty. Ltd., 
Launceston, Hobart, Burnie, Deven- 
port. Telephone: 31-2511. 
Queensland: Fred Hoe & Sons Pty. 
Ltd., 246 Evans Road, Salisbury 
North, Brisbane. 4107. 

Telephone: 47-4311. 

Wollongong: M.E.S. Pty. Ltd., Com¬ 
ponents Division, 119 Auburn Road, 
Wollongong. 2500. Tel.: 29 9377. 


Western Australia: M.J. Bateman Pty. 
Ltd., 926 Hay Street, Perth. 6000. 
Telephone: 21-6461. 

South Australia: Unbehaun & John¬ 
stone Pty. Ltd., 51 North Terrace, 
West Adelaide. 5000. 

Telephone: 51-3731. 

New Zealand: 

Upper Hutt: Standard Telephones & 
Cables (New Zealand) Ltd., P.O. Box 
40140. 

Auckland: C.R. Peoples, P.O. Box 
10097, Balmoral, Auckland 4. 
Telephone: 69-4476. 

• REGISTERED TRADE MARK 


Standard Telephones and Cables Pty. Limited an in associate 


46 


ELECTRONICS Australia, June, 1972 








+45V 


PHONO 1 INPUT PHONO 2 INPUT 


PA amplifier, cont. 


chassis via lOOpF capacitors. Similarly, the 
shield of each phono input cable is connected 
to the shield of the DIN sockets via a lOOpF 
capacitor in each case. The lOOpF 
capacitors prevent RF being radiated in¬ 
side the chassis by the input cable shields. 

The power amplifer board can now be 
assembled. All the passive components, 
with the exception of the O.luF capacitor 
should be installed first. The RF choke Ll 
consists of 20 turns of 22 SWG enamelled 
copper wire on a lin long section of VUn 
diameter ferrite rod. Remember that if a 
ferrite rod has to be cut to length, it may be 
done by filing a nick around the cir¬ 
cumference at the required point and 
snappping as if it were glass. 

The integrated circuit pins are soldered 
direct to the edge of the printed board. The 
ten pins are bent up at right-angles at the 
point where they taper suddenly. The board 
assembly can then be installed. It is sup¬ 
ported by two screws and nuts so that it has 


l /iin clearance from the chassis. The in¬ 
tegrated circuit is secured to the rear of the 
chassis by two screws. 

If the screws are over-tightened the 
chassis rear will become warped, and if this 
occurs it will not make good thermal con¬ 
tact with the metal backing of the in¬ 
tegrated circuit. To avoid this, an L-shaped 
reinforcing piece should be secured to the 
rear of the chassis with the same screws 
that hold the IC in place. Silicone jelly 
should be lightly smeared over the back of 
the IC to improve thermal contact. 

Assembly of the mixer control board is 
more straightforward. Note that the shield 
for one of the phono input cables is not 
connected to the board but is connected only 
to the shield of the other phono input cable 
at the sockets. This is to avoid earth loop 
problems. The output signal cable to the 
power amplifer is connected to two printed 
board pins to facilitate soldering. All the 
connections to the pots are made via un¬ 
shielded wire. 

Note that the complete circuit of the PA 
amplifer is connected to the chassis at one 



Above is the printed wiring board for the 
mixer control section with connections to 
the front panel control potentiometers 
shown along the top. At lower left is the 
printed wiring board for the power am¬ 
plifier showing connections to the IC. 
Boards are shown as viewed from the 
component side. 


SEMI 

CONDUCTORS 




POWER TRANSISTORS 


MICROWAVE POWER 




REFERENCE DEVICES 





LIGHT EMITTING 
DIODES AND DISPLAYS 

PHOTOSENSITIVE 

DEVICES 

INTEGRATED CIRCUITS 


LINEAR, DIGITAL, HIGH 


SCR’s AND TRIAC’s 


y See the Specialists 

in Components and Service 




Hawker Siddeley 
Electronics 


SYDNEY 93 0221, MELBOURNE 387 1899, 
BRISBANE 47 4311, ADELAIDE 46 5941, 
PERTH 71 8766. 


HSE7263/1271 


ELECTRONICS Australia, June, 1972 47 



































































































































the world famous 

Connoisseur BD2 integrated transcription 
unit lays a great foundation for top stereo 
sound. It incorporates the SAU2 high precision 
tone arm, inbuilt hydraulic cueing control 
placed conveniently at the front edge of the 
baseplate, and stop/start switch. It is 
powered by a 14 pole synchronous motor 
driving a precision-ground rubber belt, and can 
be supplied ready to install, or complete with 
base and acrylic cover. 

Connoisseur BD1 turntable, built to the same 


Interdyn specialist agents: 

N.S.W.: Encel Electronics Pty. Ltd., 260 Elizabeth St., Sydney. 
Q'ld.: Stereo Supplies, 100 Turbot St., Brisbane, 4000. 

SA.: Challenge Hi-Fi Stereo, 6 Gays Arcade, Adelaide. 

TAS.: Audio Services, 72 Wilson St., Burnie. 7320. 

VIC.: Encel Electronics Pty. Ltd., 431 Bridge Rd., Richmond. 3121. 
W A.: Albert TV & HI-FI, 282 Hay Street, Perth, 6000. 


"no compromise" specifications as the BD2, 
comes without tone arm and is fitted with a 
smaller mounting plate to permit installation of 
any type of arm. It is available ready to play, or 
in easily assembled kit form at lower cost. 

Hear Connoisseur at the selected Interdyn 
specialist agents below, or write to us for 
authoritative reviews. 


Sole Australian Distributors: 



International Dynamics (Agencies) Pty. Ltd. 

P.O. Box 205, Cheltenham, Vic. 3192. 

lease send information on Connoisseur. 

NAME . 

ADDRESS . 

.. EA8614 


48 ELECTRONICS Australia, June, 1972 















PA amplifier, cont. 


point only: this is at the 8-lug tagstrip which 
accommodates the rectifier diodes and 
some of the the transformer terminations. 
It is extremely important that details of 
shield wiring around the input sockets as 
indicated on the wiring diagram are 
followed exactly to the letter. If this is not 
done, the amplifier could be unstable, prone 
to RF pickup or just plain noisy due to earth 
loops. 

The pilot light is a neon assembly con¬ 
taining a limiting resistor, and is connected 
directly across the mains. The leads to it 
should be twisted and arranged as shown in 
the photograph and wiring diagram. In 
addition, a tinplate shield is arranged over 
the pilot assembly to stop hum radiation. 



Dimensions for the L-shaped reinforcing 
piece which assures good thermal contact 
of the 1C to the rear of the chassis. 

Both sides of the mains are switched, 
using a DPST switch. The transformer 
primary leads are terminated directly to 
the switch, as are the leads for the neon 
pilot. The switch used in the prototype was 
actually a DPDT type with one half unused. 

The mains cord should be passed through 
a grommetted hole in the rear of the chassis 


MATERIAL: TINPLATE 





- 1 "-► 






z 


z 





£ 

t~\ 


o 2 

Q 

Z 

LU 


§ 

o 

z 

m 






DIA. HOLE 





1 





"■- 1-1 / 4 "- 

-• —5/8"— ► 

- —5/8"— 


Dimensions for the hum-prevention shield 
to be mounted over the rear of the pilot 
light assembly. 


and anchored by a clamp. This can be 
secured by one of the screws which hold the 
8-lug tagstrip. 

Having assembled the amplifier, the unit 
can be switched on, with the supply lead to 
the amplifier disconnected. If the DC 
voltage across the 2200uF capacitor is more 
than 50 volts, the 256 volt tap on the trans¬ 
former should be used instead of the 240V 
connection. This will reduce the supply 
voltage slightly. 

When this is done the supply may be 
connected to the amplifier. Current drain 
with no signal should be between 20 and 50 
milliamps. If it is substantially more than 
this, the unit is probably oscillating 
supersonically. Switch off and check that 
you wiring is exactly the same as in the 
wiring diagram. 

The voltage across the 2200uF output 
(Continued on Page 113) 


PA amplfier — parts list 


1 chassis, 10Va x 8% x 3'A inches, with 
cover. 

1 reinforcing angle piece (see text) 

1 neon pilot shield (see text) 

1 power transformer, 64V centre 
tapped, at 2A AC. 

1 printed board, 72a6 

1 printed board, 72mx6 

2 3-pin DIN sockets 

1 2-pin loudspeaker socket 

2 button type microphone sockets (with 
insulating washers) 

1 fuseho/der and 1 amp fuse 
5 knobs 
1 front panel 

1 neon pilot light assembly 
1 miniature 240V DPST switch 
1 8-tug tagstrip - 

1 mains cord damp 
4 rubber feet 

SEMICONDUCTORS 

2 EM402 or BY126/200 silicon diodes 
7 BCI08, BCI48, or 2N3565 silicon NPN 
transistors 

1 TA20B power amplifier 1C (STC) 
CAPACITORS 

2 x 2200uF/ 50VW electrolytic 

1 x 250uF/ 60VW electrolytic 

3 x IOOuF/ 25VW electrolytic 

2 x IOOuF/ 6VW electrolytic 


5 x 5uF/ 72VW electrolytic 
2 x 0.22uF/ 100VW metallised polyester 
1 x 0.33uF/ 100VW metallised polyester 
3x0.1uF/ 100VW polyester 
1 x .056uF/ 100VW polyester 

1 x .047uF/ 100VW polyester 

7 x lOOpF polystyrene or ceramic 

2 x 47pF polystyrene or ceramic 
2 x 47uF/ 25VW 

1 x 47uF / 50 VW 

RESISTORS 

(all V 2 watt, 10% tolerance) 

4x 1M,3x 150K, 2 x 120K,2x 100K, 

10 x 10K, 3 x 2.2K, 2x 7.5K, 1 x IK, 

2 x 680 ohms, 2 x 560 ohms, 2 x 270 
ohms, 1 x 10 ohms, 1 x 4.7 ohms 

5 xlOK dog) potentiometers 

MISCELLANEOUS 

Mains cord and plug, shielded cable, 
hook-up wire, ferrite rod, printed circuit 
pins (2), screws, nuts, lockwashers, 
solder. 

Note; Resistor wattage ratings and 
capacitor voltage ratings are those used 
for our prototype. Components with 
higher ratings may generally be used, 
providing they are physically compatible. 
Components with lower ratings may 
also be used in some cases, providing 
the ratings are not exceeded. 


ALWAYS RELY ON R.D.S. 

SPECIALS 


Ronette mono cartridge 

with sapphire stylus $2.55 

Ronette stereo cartridge 

with sapphire stylus $3.63 

JSC1 ceramic cartridge. 

Stereo with diamond stylus $7.02 

CT-500P multimeter, 

20,000 OPV $16.10 

AS-100D/P multimeter, 

100,000 OPV $37.95 

MVA-100 multimeter, 

100,000 OPV $40.25 


The Independent Wholesaler 

RADIO 

DESPATCH 

SERVICE 

Radio and Electrical Distributors 

869 GEORGE STREET, 
SYDNEY 

(Corner George and Harris Streets) 

Telephone 211 0816, 211 0191 

Open Saturday mornings 

WANTED! 

Commission Agent 

to sell fast moving audio lines to major 
retailers and wholesalers in Sydney 
metropolitan area. Exclusive franchise 
offered. We can beat anyone's price 
and quality. 

Reply to Box X1200 

"Electronics Australia" 

26 Hunter St, Sydney 2000. 


J0FAL PRODUCTS 


Manufacturers and suppliers 
of quality printed and etched 
circuit boards y amplifier panels 
and fascias. 

(Engraved, anonidised or 
screen printed). 

Quotes for light machining 
and instrument making or 
screen printing. 

Mail orders prompt attention. 

P.O. Box 20, Essendon. 

Vic 3040. 

Phone:37-6818 or 379-2143 A.H. 


ELECTRONICS Australia, June, 1972 


49 

















































Nuclear medicine 
a the gamma camera 


The last twelve months has seen a dramatic increase in the use of nuclear 
medicine in Australia. Aided by the continual advance of electronics, the 
gamma camera has emerged as one of the most important diagnostic in¬ 
struments available to the medical profession. 


The science of nuclear medicine deals 
mainly with obtaining diagnostic informa¬ 
tion by injecting a patient with a 
radioisotope and tracing its path through 
the body. The isotope’s accumulation in 
various organs can show the physician any 
abnormalities present. 

The patient is placed under the gamma 
camera, which produces photographic 
recordings of organs and areas of the body 
containing gamma-ray-emitting isotopes. 
The photograph obtained is an ac¬ 
cumulation of dots displayed on a cathode 
ray tube, each dot representing a radio¬ 
active decay event occurring within the 
body. 

Over a short period of time, hundreds of 
thousands of dots appear and are recorded 
on film. Two photographic records are 
normally made. One is made with a triple 
lens camera equipped with a Polaroid film 
back. The three lenses provide three ex¬ 
posures, f8, fll, and fl6. The photograph 
from this camera is ready for viewing about 
about 15 seconds after the study is com¬ 
pleted. 


The other record is made with a 35mm 
camera on conventional film. This system 
provides somewhat more exposure latitude 
than the one using Polaroid film and, 
together, the two systems provide 
maximum diagnostic information. 

If an abnormality such as a tumour or 
lesion in a brain is present, it can appear as 
a much brighter region of dots as more 
isotope is absorbed by the tumour. In the 
case of a liver, the opposite can be true—i.e. 
a tumour can appear as a dull area due to 
very little radioactivity being present. 

The isotopes injected are gamma emit¬ 
ting substances and the gamma rays pass 
from the patient through a parallel-hole 
collimator (figure 1) where they enter a 
clear sodium iodide crystal. The crystal is 
disc shaped, half an inch thick and lOin in 
diameter. 

The collimator is a block of lead of the 
same diameter as the crystal and about 
lVfein thick. It is drilled with a large 
number of parallel holes (typically 4000.) It 
is mounted against the face of the crystal 


by Paul T. McQuarrie 


+Y 



-Y 


Fig 2. Explanatory diagram showing how a 
minimum of four photo tubes can deter¬ 
mine the position of a light flash on the 
crystal. 

and the holes run at right angles to this face. 

The collimator functions in lieu of 
a focusing facility. Since the crystal cannot 
be placed in contact with the organ under 
observation, but must usually be several 
inches away from it, the natural tendency 
for the particles to radiate in all directions 
would produce a meaningless image. It is 
desired that the crystal respond only to 
those particles which approach it at right 
angles to its face. The collimator achieves 
this simply because any particle which 
enters a hole at an angle to it, will be ab¬ 
sorbed by the wall before it reaches the 
crystal. 

The gamma rays which reach the crystal 
are absorbed by it and the energy is trans¬ 
ferred to become minute flashes of light 
(photons) at the point in the crystal directly 
above the location where the gamma ray 
emerged from the patient. 

The photons are seen by a hexagonal 
array of 19 photomultiplier tubes sitting 
flush on the upper surface of the crystal. 
The lower surface of the crystal is sealed to 
visible light by thin metal foil, thus the light 
reaching the photomultiplier tubes 
originates solely from the flashes within the 
crystal. 

Information regarding the position of the 
scintillation in the crystal is taken from 
the ratio of the outputs of each of the 19 
phototubes. 



Fig 7. The detector head of the camera system. Note the action of the collimator , which * Searle Nucleonics, a division of Searle 
accepts only those particles arriving a right angles to its face. Australia Pty Ltd, North Sydney, NSW. 

50 ELECTRONICS Australia, June, 1972 





























Theoretically, only four phototubes would 
be required to determine position. Four 
phototubes placed at the extremities of two 
diameters at right angles drawn across the 
crystal (see figure 2) would be sufficient to 
determine the position of any scintillation of 
light within the circular crystal. 

If the light pulse occurred at point A, the 
centre of the crystal, each tube would 
record the pulse equally and the outputs of 
each tube would be the same. The point A is 
the only position in the crystal where the 
outputs of all four tubes would be the same. 

Similarly, at point B, tubes 2 and 4 would 
give equal outputs, whereas tube 1 would 
give a larger output, and tube 3 a smaller 
one than tubes 2 and 4. Point B is the only 
position in the crystal where this rela¬ 
tionship between the outputs exists. 


Noise levels in phototubes, however, 
sometimes approach the low signal level 
from light pulses seen on the far edge of the 
crystal. For this reason, more than four 
tubes are used, in this case 19, to overcome 
the problem of low signal level. 

The output of each tube is fed to individual 
preamplifiers, the signal is passed through 
a resistive matrix, and the X and Y 
directional components are extracted. The 
signal then leaves the “head” via four 
lines4-X, -X, +Y, -Y. (Figure 3). 

Entering the console the signal is split, 
one part being used to provide positional 
information, and the other part to provide 
total energy information concerning the 
original disintegration. 

The total energy information path goes to 
a summing circuit, where the four signals 


The camera in operation. The detector head 
is on the left, against the patient's head, 
and part of the control panel, with camera, 
on the right. 

are arithmetically summed. The resultant 
signal is directly proportional to the gamma 
energy of the original disintegration. 

The system is required to differentiate 
between legitimate and false pulses. False 
pulses may be due to photomultiplier noise, 
or other rays given off by the isotope but 
which are not required for the study. 

The energy of the gamma particles, as 
sensed by a pulse height analyser, is used to 
provide this discrimination. The analyser 
uses tunnel diodes as upper and lower 
discriminators and for the pulse to emerge 
from the analyser the pulse height must be 
more than the lower discriminator, yet less 
than the upper discriminator. 

The effectiveness of this system is aided 
by the fact that, in many newly designed 
synthetic isotopes, a large percentage of the 
disintegration occurs at the one energy 
level, or very close to it. 

Output from the pulse height analyser 
goes to a scaler and to the control grid of the 
CRT. The CRT is normally turned off or 
“blanked”, and the pulse from the analyser 
turns the tube on. 

The positional information goes to the X 
and Y positioning circuits. The four signals 
are amplified individually and fed to dif¬ 
ferential amplifiers. Output trom these is 
applied to the X and Y deflection plates of 
the CRT. 

Thus, as the energy channel turns on the 
CRT to produce a spot on the screen, the 


Fig 3. Block diagram of the complete gamma camera system. Note the position¬ 
ing circuits which generate deflection voltages for the CRO plates, and the 
summing circuits which generate intensity voltages for the CRO grid. 


OUTPUT PULSE FROM PULSE HEIGHT ANALYZER IS 
1) RECORDED BY DUAL SCALER TIMER AND 2) UN¬ 
BLANKS THE CATHODE RAY TUBE TO ALLOW THE X 
AND Y POSITIONING INFORMATION TO DISPLAY THE 
DOT IMAGE 


ENERGY CHANNEL 


Z-PULSE SUMMING 
CIRCUITS 


PULSE HEIGHT ANALYZER - 


® ® ® ® ® ® 

DUAL SCALER/TIMER 


OUTLINE OF DOT IMAGES 
ACCUMULATED OVER PERIOD 
OF TIME ON DISPLAY SCREEN 


Z-PULSE INPUT 


RECORDING CAMERA 



PHOTOGRAPH SHOWING THREE 
SEPARATE IMAGES WITH VARYING 
DEGREES OF CONTRAST OF THE 
ORGAN OF INTEREST 


ORGAN OF INTEREST 


GAMMA RAYS 


ELECTRONICS Australia, June, 1972 


51 


































































GOLDRING 

Engineering (A’asia) Pty Ltd. 


New South Wales: 26 Ricketty Street, Mascot 2020. Telephone 67 6088. 
Canberra: 19 Molonglo Mall, Fyshwick, A.C.T. 2604. Telephone 95 8248. 
Victoria: 162 Pelham Street, Carlton 3053. Telephone 347 5177. Queens¬ 
land: 32 Balaclava Street, Woolloongabba 4102. Telephone 91 4972., 

South Australia: 207 Flinders Street, Adelaide 5000. Telephone 
23 3488. Western Australia: 32 Northwood Street, Leederville 600/^ 

Telephone 8 4988. 


. TKo* 


.... / 


^ o. 

A.°V. 




ELECTRONICS Australia, June, 1972 


52 


















Fig 4. The bright white band represents a 
large number of events at that energy level. 
The black patch is the "window" which 
observes this particular energy level. 


positioning circuits apply the appropriate 
voltages to the deflection plates to correctly 
locate the spot, relative to the original posi¬ 
tion on the crystal. 

Each pulse that reaches the CRT is also 
counted on one of two separate scalers. The 
duration of each study is determined by 
either a timer, or, more commonly, by 
nominating the total number of dots 
required on the film. 

The latter method is preferred because 
the results obtained are independent of the 
isotope dose administered, and, to a lesser 
extent, independent of organ and patient 
size. 

Before a study can be performed, the 
system must be adjusted so that disintegra¬ 
tions due to the isotope will pass through the 
pulse height analyser. To do this a “Spec¬ 
trum” mode is provided which gives a 
visual presentation of all the pulse heights, 
both wanted and unwanted, on the CRT. 
(Figure 4.) The black rectangle represents 
the “window” through which the accepted 
pulses will pass, the top edge depicting the 
upper discriminator and the bottom edge 
the lower discriminator. 

The bright band in figure 4 represents a 
large number of events occurring at that 
particular energy. The window bandwidth 
can be adjusted from 0% to 35% of the 
isotope energy peak. 

To adjust the pulse height, an “Isotope 
Peak” control varies the high voltage ap¬ 
plied to the photomultiplier tubes on the 
crystal. This varies the output from each 
tube, so that the band can be centred over 
the window. All of the pulses passing 
through the window are fed -to the CRT 
from which the photographic recording is 
made. 

Normally, organs are studied from more 
than one position. In the case of brain 
studies, four views are taken, posterior 
(back of head), anterior (front of head), and 
left and right lateral. Occasionally a vertex 
(top of head) view is made. 


Gamma cameras will be as common as X-ray ... 


From these views, accurate positional 
information of lesions is obtained. Figure 5 
shows a tumour in the frontal area of the 
brain. Taken about two hours after injection 
of a radioisotope, the photograph shows the 
brain cavity as a dull area with the tumour 
absorbing more isotope and consequently 
appearing as a bright region. 

The ability of the isotope to concentrate in 
a tumour is a characteristic of the com¬ 
pound in which the isotope is contained. For 
brain studies, this compound is sodium 
pertechnetate, containing technetium. 

Technetium is a manufactured isotope 
derived from molybdenum and is used in 
various compounds for studies of most 
organs. Produced at the Australian Atomic 
Energy Commission’s establishment at 
Lucas Heights in Sydney, the compounds 
containing the isotope are prepared daily 
and delivered to the various hospitals 
around the city. 

The isotope of technetium is a short lived 
one, with a half-life of six hours, giving a 
high photon yield, and making for short 
study times. Also, because of the short half- 
life, the radiation dose is insignificant to the 
patient. 

The isotope is available at present in four 
different compounds, of which three are 
specific to particular organs. Sodium 
pertechnetate goes to most organs in the 
body and is used mainly for brain studies. 
Figure 6 shows a lung study using macro- 
aggregated ferrous hydroxide (MAFH) 
containing technetium. The MAFH par¬ 
ticles are somewhat larger than the 
diameter of the capillaries in the lungs. As 
blood goes from the veins to the lungs 
(through the heart), the particles are 
removed from the blood in the lungs, and go 


to no other organ in the body. The particles 
decompose after a short time in the lungs 
and are removed. 

Figure 7 shows a kidney study using 
technetium gluconate. The gluconate is 
filtered from the blood by the kidneys and 
passes to the bladder. 

Other compounds containing different 
isotopes are used for less common studies, 
such as indium 113 chloride for placentas (in 
pregnancies) and fluorine 18 in bone studies. 

In some organ studies, such as lungs and 
kidneys, it is useful to determine relative 
function of each half of the organ. To ac¬ 
complish this, the camera provides a 
facility to split the field of view down the 
centre, electronically, and the pulses from 
each half are counted in separate scalers. 
Thus, at the end of the study, the number of 
counts in each scaler gives a ratio of the 
performance of one half of the organ to the 
other. This is particularly useful in kidney 
studies. 

Another useful facility of the camera is to 
record the study continuously via a 
videotape recorder. The complete study can 
then be played back at a convenient time 
and the photographic recordings obtained. 

An advantage of this facility is that areas 
of interest may be constructed so as to view 
the information returning from the tape in 
selected areas only, making for more in¬ 
formative results. 

As the science of nuclear medicine is 
recognised better as a non-traumatic, high 
information diagnostic procedure, more 
gamma cameras will appear in hospitals 
around Australia, when studies under the 
camera will be almost as common as 
present day X-ray studies. 0 



Fig 5 (above). View of a brain containing 
a tumor. The tumor appears as a bright 
spot near the centre. Bright area at the 
bottom represent facial tissues, etc. 

Fig 6. (above right) Front view of a pair of 
lungs showing a non-functional (dark) area 
in the lower part of the right lung. 

Fig 7 (right). Front view of a pair of kidneys, 
with the bladder below them. A blockage in 
the (patient's) left ureter shows as a bright 
patch. 

(Gamma camera photographs on this page 
are reprinted by courtesy of the Royal 
Prince Alfred Hospital, Sydney.) 



ELECTRONICS Australia, June, 1972 53 










Miniature Radios — A Challenge 

What is your approach when a customer produces a foreign brand 
miniature radio which “doesn't go"? Do you accept the challenge, or do you 
consider they are not worth handling? This is one of the problems discussed 
this month. 


There is no doubt that these little devices, 
particularly the odd types brought back 
from overseas, present a sticky problem for 
the serviceman. Unless the fault is a very 
elementary one, servicing may be quite 
uneconomic. 

On the one hand, they are purchased for 
only a few dollars overseas, and the owners 
invariably tend to relate service charges to 
the purchase price. Against this, 
replacement parts are generally as scarce 
as the proverbial hens’ teeth, so that 
repairs, if possible at all, invariably involve 
time consuming improvisations. As a 
result, costs mount rapidly, often to a figure 
far in excess of the original price. 

Only if the customer is fully aware of this, 
and willing to meet these costs, is it 
worthwhile the serviceman even looking at 
the set. 

For all these reasons, most servicemen 
tend to shy away from them. A few, on the 
other hand, seem to relish the challenge, 
and gear their working procedures to cope 
with the problems. 

This is no simple task. Among the things 
to be organised are supplies of spare parts, 
either from the importers or, in many 
cases, directly from overseas; service data, 
again often directly from the makers; test 
equipment, such as regulated and metered 
power supplies; and, most important of all, 
as much background and general 
knowledge about the circuits and com¬ 
ponents involved as possible. Typical of this 
latter requirement is the need to know 
which components are interchangeable 
between one brand and another, or what 



locally made components, including 
transistors, can be substituted for those 
originally employed. 

Among the few who have committed 
themselves in this manner is a fellow ser¬ 
viceman whose name readers may have 
already seen in advertisements in this 
magazine — Peter Broughton. At my 
suggestion he plans to select some of his 
more interesting cases and submit them for 
publication from time to time. Here is his 
first one, a typical example of the problems 
I have outlined. 

The customer was a dear old lady who 



The autodyne circuit of the set in this story. 
With minor variations it is typical of most 
current designs. 

begged me almost literally with tears in 
her eyes, to repair a small portable radio. It 
transpired that she had recently returned 
from an overseas trip and had brought back 
six of these sets; one for each of her six 
grandchildren. They had cost her 
something like four dollars each. 

When one of them had subsequently failed 
she had taken it to another service 
organisation who, having examined the set. 
advised that they were unable to repair it 
because they did not have the appropriate 
spare part However, they pointed out that, 
had they been able to do the job, it-would 
have cost around $15. She added, “They said 
I would be mad to pay out that kind of 
money to repair something which only cost 
four dollars in the first place.” 

As diplomatically as I could, I was forced 


to agree with them. Still, for what I suppose 
can only be described as sentimental 
reasons, she wanted the set fixed. The best I 
could promise was that, if I could fix it, it 
should not cost the figure previously quoted, 
but could still cost more than the new price. 
She accepted this situation and told me to 
see what I could do. 

The set was a fairly standard design, 
which I have seen under various brand 
names, made in both Hong Kong and 
Taiwan. A significant characteristic is that 
they all operate from a single UM 3A cell ; a 
total supply of 1.5 volts. It was only because 
I had some knowledge of the design that I 
felt reasonably confident that I could get it 
going again. 

On switching the set on, my first reaction 
was that it was quite lively and rearing to 
go. The only thing wrong was that it 
wouldn't receive any stations. The most 
likely explanation was that the local 
oscillator had failed. 

There are a number of simple tricks one 
can use to confirm such an assumption. One 
is to use the signal generator as a substitute 
for the local oscillator. I usually set the 
receiver to 2BL, couple the output of the 
generator loosely to the aerial circuit of the 
set, and set the generator to 2BL plus 
455KHz. (740 plus 455 is 1195) 

If the only fault is local oscillator failure, 
the set will bring in signals, and not only 
from 2BL but from other stations as the 
signal generator is set to the appropriate 
frequency. 

Another trick is a variation on this, in that 
a second set is used in place of the 
generator. In this case the two sets can 
usually be coupled quite adequately by 
simply arranging that the two aerial coils 
and rods are as close as possible. 

Satisfied that it was the local oscillator, I 
checked off the likely causes; shorted 
oscillator gang, shorted trimmer, open 
circuit loop winding, no voltage on the base 
or the transistor, or our old friend an open 
oscillator coil. 

A quick visual check revealed some 
“claw marks” around the oscillator coil. 
Pretty obviously, this was where someone 
else had been working, almost certainly the 
previous serviceman the owner had men¬ 
tioned. A quick check with the ohmmeter 
confirmed my fears; the coil was open 
circuit between the tap and the chassis end 
of the base winding. 

What does one do in a case like this? The 
set is not available on the local market and, 
as a result, I carry no spare parts for it, nor 
do I know of anyone who does. On the other 
hand, it is a common problem, and I have 
developed a routine for tackling it. 

Any possible solution is based on the fact 
that one autodyne circuit is very much like 
another, apart from a few' minor dif¬ 
ferences, and one autodyne oscillator coil is, 
likewise, very like another — at least 
electrically. Unfortunately there appears to 
be very little standardisation among the 
Japanese manufacturers, and the five pin 
connections are likely to be in one of the 
umpteen possible combinations. Similarly, 
the size and mounting arrangements may 
differ. 

In cases like this I am forced to salvage 
what I can from sets already discarded for 
other reasons. And where foreign sets are 
concerned I never throw anything away. 
From this stock I select the coil which is as 
close as possible in shape and size to the 


54 


ELECTRONICS Australia, June, 1972 




































original. 

Then one has to determine the correct pin 
connections. The individual windings can be 
identified with an ohmmeter, as can the 
tapping on the tuned winding. To identify 
the tap, first find which two of the three 
terminals presents the highest resistance, 
usually from 5 to 12 ohms. Since this must 
represent the total winding, the remaining 
terminal is the tap. Finally, determine 
which terminal is closest to the tap in terms 
of resistance. This will be the “earthy” 
terminal, and the remaining one must 
connect to the oscillator gang. 

By this means this winding can be 
correctly connected, leaving only the 
feedback winding to determine the correct 
phase. Of course, by Murphy’s Law, this 
will always be connected the wrong way the 
first time, even if one tries to circumvent 
this by connecting it the way you think it 
should be connected the second time, the 
first time. 

This set set was no exception, and 1 had to 
transpose the connections before it would 
work. But it did work, although sounding a 
little sick. From then on it was mainly a 
matter of alignment to put back into place 
the slugs which had been fiddled with by the 
previous serviceman. 

Why people fiddle with IF and oscillator 
slugs when they can’t find any ovbious fault 
in a set is beyond me. Yet they do, and 
surprisingly often. In fact, one of the first 
things I look at in these little sets is the IF 
transformers. If the slugs have been wound 
out further than their normal position, I 
reckon it’s pounds to peanuts that someone 
has been having a fiddle. Since this kind of 
fiddling never cured a dead set to my 
knowledge, all they succeed in doing is 
creating a second fault on top of the original 
one. 

Anyway, the set came good progressively 
as I peaked up the various sections and 
when I had finished it was performing 
exceptionally well. 

As for the dear old lady — well, she 
seemed happy beyond belief, just to have 
the set working again. Even if it did cost her 
more than the price of the set. 

Oh well, happiness is many things to 
many people. 

From my own service bench I have a 
story about a domestic TV receiver. This 
was a National set, model TW520, designed 
in Japan but assembled in Australia. It is a 
valve set equipped with a 25in (635mm) 
picture tube. The symptoms were lack of 
picture height, there being about one inch of 
black border top and bottom. While it was 
possible to restore most of the height by 
means of the height control, this left nothing 
to spare and was obviously not the answer. 
In addition, it upset the vertical linearity 
quite seriously. 

In the normal way my first test would be 
to replace the valve or valves associated 
with this part of the circuit. In this case it 
was a triode-pentode as vertical oscillator 
and output valve respectively, but the type 
number, 18GV8, had me beaten. In fact, 
most of the valves in the set would have 
been beyond my stock, having been selected 
to suit a heater circuit operating directly 
from 110V. The Australian version of the set 
is equipped with a transformer to suit the 
240V mains. 

For this reason I decided to make a 
preliminary voltage check first. If this 
showed no discrepancies from the service 


manual, I would order the necessary 
valves. Even if they ultimately proved 
unnecessary, they would be useful ones to 
have on hand. 

My first check was at the plate of the 
triode (oscillator) section. According to the 
circuit this should have been 108V but was 
only 90. While enough to make one 
suspicious, it was hardly enough to regard 
as a major symptom. My next check point 
was at the hot end of the “HEIGHT” pot 



The relevant portion of the TV receiver 
circuit, showing the 680pF capacitor which 
proved to be faulty. 


which, from the circuit, should have been at 
560V. Instead it was only 450. 

This was a much more tangible 
discrepancy, particularly as a closer 
examination of the circuit confirmed that 
this was virtually the B plus boost supply 
line. 

As a first check I disconnected this boost 
line from the height pot and noted that it 
remained low. Whatever the fault was, it 
didn’t seem to be associated with any ex¬ 
cessive drain around the vertical oscillator. 

So what was next? I traced the boost line 
through the circuit and came to pin 3 (anode 
1) of the picture tube. The diagram showed 
a 680pF capacitor connected from this line 
to the line from pin 4 (anode 3 or focusing 
anode). This line, in turn, went to one of four 
terminals providing a selection of focusing 
voltages, being zero (chassis), two values 
derived from the HT line, and the boost line. 
In this case the chassis terminal had been 
used. 

The 680pF capacitor had me intrigued. It 
was a rather unusual component in that 
part of the circuit and I couldn’t figure out 
what it was for. More to the point, I began 
speculating on the effects if it was leaky. 
With one end connected to chassis and the 
other end to the boost line, any significant 
leakage could be a serious drain on the 
boost supply. 

Because it was easiest to do, I simply 
shifted the focusing electrode lead from the 
chassis terminal to the boost line terminal, 
thereby putting the two ends of the 
capacitor at the same potential. The effect 
was immediate. The focus may not have 
been optimum, but the picture jumped back 
(Continued on Page 113) 


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HAYMARKET 

PHONE SYDNEY 211 5077 


Entrance from courtyard off 
Little Hay Street. 


Trade Enquiries given prompt 
attention. 


ELECTRONICS Australia, June, 1972 


55 






















Microwaves for 
the radio amateur — 2 

The second of a short series of articles written in an attempt to stimulate 
more activity by radio amateurs on the microwave bands. In this chapter 
the author deals with waveguides and the way in which electromagnetic 


energy propagates along them. 

by DES CLIFT, VK2AHC* 

In the first article reference was made to 
various terms and items connected with 
microwave engineering. As some readers 
may be unfamiliar with these, a brief ex¬ 
planation of the more common ones follows. 

In the part of the electro-magnetic 
spectrum under consideration, waveguides 
are frequently encountered. Usually 
waveguides are hollow rectangular tubes, 
and are basically used for conveying 
microwave energy from point A to point B 
with as low a loss as possible. Normally 
they are drawn tubes of brass, copper, 
aluminium or silver, but can be fabricated 
by milling or electroforming processes. 
There are important variations such as 
semi-flexible and flexible rectangular, 
double or single ridge, and circular 
waveguides. All, however, possess similar 
properties and operate in more or less the 
same manner. 

Table II lists some of the waveguides that 
are used, ranging from the higher UHF 
bands right up to the region where radio and 
infra-red light waves merge. This is quite a 
large slice of the spectrum and, although 
their use at either end of this range is 
reasonably specialised, about half of the 
range is in very wide use commercially. 
Note that 300GHz (1 millimetre 
wavelength) is about the shortest radio 
wave used. For comparison the longest 
infra-red light waves (0.4 millimetre 
wavelength) have a frequency of about 
900GHz. 

At the lower frequencies the size of the 
waveguide becomes impractical. Very 
conveniently, at these frequencies the 
losses in the coaxial cables are still 
reasonably low. The WR 2100 type is about 
the largest size of tube used in practice, and 
this has similar dimensions to the small air 
ducting seen in offices and industry. 

At the high frequency end, the limitations 
are mechanical, and also the difficulty in 
producing the energy itself is no small 
problem. Amateur use of waveguide is, as 
has been pointed out, usually limited to the 
10,000 MHz band. 

There are various systems of numbering 
waveguides, as shown in Table II. The UK 
has adopted the “WG” numbering system, 
starting at 00 up to 32 or so. 

In the United States there are three main 
systems used: 

(a) EIA system, where each size is given a 

WR number which is the inside long 


*6 Gilles Crescent Dee Why, NSW 2099 
56 ELECTRONICS Australia, June 


dimension in hundredths of an inch, i.e., 
WR2100 is 21in x lOVfcin inside. 

WR10 is O.lin x .05in inside. 

WR90 (standard X band guide) is 0.9in x 
0.4in inside. 

(b) JAN types, having RG numbers in no 
logical sequence, but with separate 
numbers for different materials (brass, 
copper, aluminium, etc). 

(c) I.E.C. system, in which the numbers 
are ten times the centre frequency in 
thousand of megahertz (GHz) of the 
recommended band of use, ie, IEC100 is 10 
x 10GHz. Thus WG16, WR90, and IEC100 
are the same physical size and are 
suitable for 10,000 MHz. 

Various features should become apparent 

as a result of a perusal of Table II: 

(1) That a large number of tubes is 
required to cover the whole range. 

(2) That the size of the tube varies con¬ 


siderably, the size in fact being propor¬ 
tional to the wavelength. A lower limit of 
frequency could be said to be set by the 
size becoming impracticably large. 

An interesting point, which results from 
this, and is of very great practical use, is 
that since a waveguide is frequency sen¬ 
sitive, it can be used as a highly accurate 
and reliable attenuator. Such an attenuator, 
known as a “waveguide beyond cut off” 
type is produced by simply using a 
waveguide somewhat smaller than' would 
be normally used at the operating 
frequency. The operation of such a device 
will become apparent as a result of the 
discussions following. 

It may seem strange that it is necessary 
to vary the dimensions of waveguide to suit 
the frequency used, and that waveguide of a 
certain size can attenuate signals. After all, 
there is no similar restriction (within 
limits) when open wire lines or * coaxial 
cables are used, and at first sight the same 
form of electromagnetic wave motion is 
used to propagate energy throughout the 
spectrum. 

It is reasonable to assume therefore that 
waveguide operates in a different manner 
to coaxial cable, and open wire line. 
Readers are probably aware that in free 


TABLE II: WAVEGUIDE SIZES 


Internal 

Dimensions 

(Inches) 

Frequency 

Range 

(GHz) 

Official waveguide designations 

Band 

Letter 

U.K. 

(RSCS) 

U.S.A. 

(EIA) 

U.S.A. 

(JAN) 

U.S.A. 

(1 EC) 

21.0 x 10.5 

0.35-0.53 

WG0 

WR2100 




1 

18.0x9.0 

0.41-0.625 

WGl 

WR1800 

RG-201 / U 


| 


15.0x7.5 

0.49-0.75 

WG2 

WR 1500 

RG-202 / U 



> U.H.F. 

11.5x5.75 

0.64-0.96 

WG3 

WR1150 

RG-203 / U 



f 

9.75 X 4.875 

0.75-1.12 

WG4 

WR975 

RG-204 / U 


J 

1 

7.7 x 3.85 

0.96-1.45 

WG5 

WR770 

RG-205 / U 


1 

I 

6.5x3.25 

1.12-1.7 

WG6 

WR650 

RG-69 / U 

R14 

1 

[ L 

5.1 x 2.55 

1.45-2.2 

WG7 

WR510 


R18 

J 

I 

4.3x2.15 

1.7-2.6 

WG8 

WR430 

RG-104 / U 

R22 

1 

I 

3.4 x 1.7 

2.2-3.3 

WG9A 

WR340 

RG-112/ U 

R26 

1 

L s 

2.84 x 1.34 

2.6-3.95 

WG10 

WR284 

RG-48 / U 

R32 


f 

2.29 x 1.145 

3.3-4.9 

WGl 1A 

WR229 


R40 


1 

1.872x0.872 

3.95-5.85 

WG12 

WR187 

RG-49 / U 

R48 

1 

1 

1.59x0.795 

4.9-7.05 

WG13 

WR159 


R58 

1 

r c 

1.372x 0.622 

5.85-8.2 

WG14 

WR137 

RG-50 / U 

R70 

J 

I 

1.122x0.497 

7.05-10.0 

WG15 

WR112 

RG 51 / U 

R84 

1 

L v 

0.9 x 0.4 

8.2-12.4 

WG16 

WR90 

RG-52 / U 

R100 

J 

r * 

0.75 x0.375 

10.0-15.0 

WG17 

WR75 


R120 

j 

0.622x0.311 

12.4-18.0 

WG18 

WR62 

RG-91 / U 

R140 


0.510x0.255 

15.0-22.0 

WG19 

WR51 


R180 

}k 

0.420x0.170 

18.0-26.5 

WG20 

WR42 

RG-53 / U 

R220 


[ 

0.340x0.170 

22.0-33.0 

WG21 

WR34 


R260 

1 

r Q 

0.280x0.140 

26.5-40.0 

WG22 

WR28 

RG-96/ U 

R320 

j 


0.224 x 0.112 

33.0-50.0 

WG23 

WR22 

RG-97 / U 

R400 


0.188x0.094 

40.0-60.0 

WG24 

WR19 


R500 


0.148x0.074 

50.0-75.0 

WG25 

WR15 

RG-98 / U 

R620 


0.122x 0.061 

60.0-90.0 

WG26 

WR12 

RG-99 / U 

R740 


0.100x0.050 

75.0-110.0 

WG27 

WR10 


R900 


0.080 x 0.040 

90.0-140.0 

WG28 

WR8 

RG-138/ U 

R1200 


0.065 x 0.0325 

110.0-170.0 

WG29 

WR7 

RG-136/ U 



0.051 x 0.0255 

140.0-220.0 

WG30 

WR5 

RG-135/ U 



0.043X0.0215 

170.0-260.0 

WG31 

WR4 

RG-137 / U 



0.034x0.017 

220.0-325.0 

WG32 

WR3 

RG-139 / U 




1972 

















Fig-3 above shows a transverse electromagnetic (TEM) wave , as found in free space. By 
convention the E-field defines the polarisation. 



up ® 


EMAX 


DOWN © 

(a) WHITEPAPER 


AND TEM WAVE 2 = 6" ON PAPER 
(b) TRACING PAPER 


IXS>CX>(S> 

IXXXSX^> 

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U_ X.- 

^ MPAPI V 1 9 "~ 


XI 

X2 


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• = AREAS OF ZERO E AND H 
(0 TRACING PAPER 


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Fig. 4 SYNTHESIS OF METHOD OF TEol (H WAVE) PROPAGATION IN A WAVEGUIDE 


space, what is called a transverse elec¬ 
tromagnetic or TEM wave provides the 
means of transmission. Inside a coaxial 
cable, a strip line, or an open wire line there 
is a similar wave form, modified slightly by 
the dielectric material and the geometry. In 
these cases it is usually referred to as the 
“principal” wave. The E and H vectors are 
perpendicular, and both are perpendicular 
to the direction of propagation. Fig. 3 
illustrates this point. 

In a waveguide a wave motion that again 
has E and H perpendicular is also involved, 
but in this case there are also components of 
either E or H which are in the direction of 
propagation, and it is because of this that: 

(i) The lossy dielectric (loss proportional to 
frequency) and the less lossy inner 
conductor (loss proportional to square 
root of frequency) of the coaxial cable can 
conveniently be dispensed with. 

(ii) A wave motion which requires a 
frequency sensitive conducting system 
has been produced. * * 

One of the best ways of visualising the 
type of wave motion existing in a waveguide 
is to consider two coherent TEM waves 
interfering, as detailed in Chapter 2 of the 
book “Wave Guides” by*L. G. Huxley. 
(Cambridge Press, Modern Radio 
Techniques series). This method shows the 
formation of the required waveguide 
“mode” of transmission by algebraically 
summing the fields at various points in an 
area in which these two coherent TEM 
waves pass in different directions. 

First, however, it is essential to 
remember certain basic conditions 
(referred to as “boundary conditions”) 
which must be fulfilled in order for an 
electric or magnetic field to be able to exist 
at a restricting boundary. These are: 

(i) When an electric field meets a boun¬ 
dary, it must be at right angles to it. 

(ii) When a magnetic field meets a boun¬ 
dary it must be tangential to it. 

Usually, but not always, the boundary is a 

metallic conducting surface. Thus, the 
simple TEM wave of Fig. 3 can quite well be 
enclosed between two parallel plates, as in a 
strip line, but cannot exist if a further two 
plates are added to complete a rectangle 
(ie, to produce a waveguide) since the 
conditions above are then violated. 

In order for the electromagnetic energy to 
be able to exist and propagate down a closed 
waveguide pipe, it must really consist of 
two TEM components which are both ef¬ 
fectively propagating at a certain oblique 
angle to the waveguide axis. In effect the 
two components “bounce” along the in¬ 
terior walls of the waveguide, mutually 
interfering in such a way that they cancel in 
the planes of the two walls which would 
normally be parallel to the E field of a 
single TEM wave. 

The writer has evolved a relatively easy 
method of putting over this idea to 
amateurs or groups with widely varying 
mathematical and practical knowledge and 
this is recommended to the reader who 
would really like to understand the 
various aspects of waveguide operation. It 
involves the use of three equal size sheets of 
paper — one white, the other two tracing. 

The first TEM wave component in cross 
section is drawn as in Fig. 4(a) on a sheet of 
white drawing paper about 24in x 15in. This 
wave, as noted previously, is moving in 
space with a velocity just under 3 x 10 10 
cm / sec. In these sections the oblique lines 


represent the magnetic field, with the thick 
lines for H max (H) and the thin dotted lines 
for H min (Ho). The circles represent the 
electric field, perpendicular to the paper, 
marked in the usual conventions. E is the 
maximum, Eo is the minimum. 

Note that the maxima and minima of the 
magnetic and electric fields occur together. 
Thus the solid lines really represent not only 
sideways cross-sections of planes of 
maximum magnetic field intensity, but also 
end-on cross-sections of planes of maximum 
electric field intensity. Similarly the dashed 
lines represent planes where both the 
magnetic and electric fields are at 
minimum intensity. 

The second TEM wave component is 
produced on tracing paper, cut to the same 
size, by lightly copying only the spacing and 
lines of the first. This sheet is then reversed 
and a second series of thick and thin lines, 
and dots and crosses is drawn (Fig. 4b). In 


this way equal sizes of paper are used from 
the outset, and tracing simplifies the 
duplication of spacings and angles. 

The third sheet of paper (also tracing 
paper) is now placed over the first two. It 
should become apparent, after an initial 
observation, that there are various places 
where the electric fields add, ie, where 0 
and 0 lines cross, or ® and ® lines cross. 
There are also various places where the 
electric fields cancel, ie, where O and ® 
lines cross. 

In fact it will be found that there are 
regularly spaced planes (represented by 
horizontal lines on our diagram) over which 
the electric fields everywhere cancel. In 
between these planes the magnetic fields 
tend to interact in such a way that they form 
themselves into chains of closed loops, the 
sides of which are tangential to the planes of 
zero electric field intensity. The ends of the 
magnetic loops interlock, and it is at these 


ELECTRONICS Australia, June, 1972 57 



















































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points that the electric fields add to produce 
maxima. 

If we remember the boundary conditions, 
it should be evident that the planes of zero 
electric field intensity produced by the 
interaction of the two TEM wave com¬ 
ponents would be ideal positions for con¬ 
ducting waveguide walls. These positions 
are indicated in Fig. 4(c) as XI, X2, . . . X5. 
Conducting planes placed at any two of 
these positions could be used to confine the 
wave energy in between, without in any way 
conflicting with the boundary conditions. 

Generally the waveguide walls coincide 
with two adjacent zero-field planes, so that 
they enclose a single “chain” of the elec¬ 
tromagnetic loops. This is the situation for 
the basic or “principal” mode of waveguide 
propagation; it is possible for the 
waveguide walls to enclose two or more 
chains of loops, but this corresponds to 
“higher order” propagation modes. 

At this stage we should perhaps look at 
the significance of the angles formed be¬ 
tween the direction of propagation of each 
of the basic TEM wave components and 
their “chain-wave” resultant which 
propagates along the waveguide 
(horizontally from left to right in Fig. 4). In 
fact the two angles are the same. 

From the experiment of Fig. 4 it should 
become apparent that this “bouncing 
angle” (designated alpha) and the 
wavelength of the original TEM wave 
components (designated lambda) together 
determine the distance between the planes 
of electric field cancellation. For a given 
distance between the waveguide conducting 
walls, and for any particular wavelength of 
the electromagnetic energy, there will only 
be one angle alpha which will result in the 
distance between the planes of field can¬ 
cellation corresponding to the waveguide 
height, and this is of course necessary if the 
boundary conditions are to be satisfied. 

What does this really mean? Simply that 
in order to exist in the closed confines of a 
waveguide, the electromagnetic energy 
must effectively split itself up into two TEM 
wave components which bounce back and 
forth between the waveguide walls at an 
angle rigidly determined by the frequency. 
In fact the angle is inversely proportional to 
frequency — the higher the frequency, the 
smaller the angle, and conversely the lower 
the frequency the larger the angle. 

In the direction of increasing frequency 
there is virtually no limit — in other words, 
there is basically no reason why energy of 
extremely high frequency cannot exist and 
be propagated along any waveguide, even 
one with large dimensions. There may be 
practical difficulties in generating the 
energy and getting it into and out of the 
waveguide, but no fundamental barriers. 

On the other hand, there is a fundamental 
barrier in the direction of decreasing 
frequency. For any given waveguide, the 
angle alpha must increase as the 
wavelength of the energy is increased. A 
limit is reached when alpha finally reaches 
90*: at this angle, the distance between the 
planes of electric field cancellation 
becomes equal to a half wavelength. 

At this frequency the boundary conditions 
can still be satisfied (just!), so that the 
electromagnetic energy can still exist in 
the waveguide. But there is one problem: as 
the two TEM components must bounce back 
and forth at an angle of 90? to the waveguide 
axis and walls, they have no component of 


58 

















FLANGES A 5.65GHz 

B 10GHz (SCREWED RING) 
C 10GHz (BOLTED) 

D 21GHz 


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COAXIAL 
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velocity along the guide. So the energy is 
unable to propagate along. For this reason 
the frequency where one half-wavelength 
equals the height of the waveguide is known 
as the “Cutoff frequency” (fc) for that 
waveguide. 

It is not possible for energy to be confined 
in a waveguide if its frequency is below the 
cutoff frequency for that guide, simply 
because there is no way in which it can 
bounce between the walls without its 
electric field component being short- 
circuited. In other words, the boundary 
conditions cannot be met. 

From Fig. 4(c) it may be seen that the 
energy travelling along the waveguide has 
an effective wavelength equal to two of the 
magnetic loops. This is known as the 
“waveguide wavelength” (xg)- This length 
is always greater than the free-space 
wavelength, and the ratio between the two 
increases as the bouncing angle increases 
— ie, at frequencies approaching cutoff. 

This wavelength is of great importance as 
it is the one that is actually measured with a 
slotted waveguide and the one that controls 
the physical dimensions that components 
are designed around. Fortunately for 
amateurs, highly accurate measurements 
of ^g are seldom required for amateur 
work. 

Because the waveguide wavelength is 
always longer than the free-space 
wavelength, the theoretical “phase 
velocity” with which the energy propagates 
along a waveguide is greater than the speed 
of light. But the actual velocity of 
propagation of the energy is in fact always 
lower than the speed- of light, because the 
components making up the wave are 
bouncing back and forth as well as moving 
along. In other words, the “chain of loops” 
moves along the guide only at a rate 
corresponding to the components of the 
original TEM wave velocities in the 
direction of the waveguide axis. See Fig. 
4(d). 

In fact the actual velocity of propagation 
is proportional to frequency, for a given 
guide, and reduces as the frequency is 
lowered. As the cutoff frequency is ap¬ 
proached, the velocity reduces in an ex¬ 


ponential manner, and finally falls to zero. 

The two waveguide “top” and “bottom” 
walls that we have been considering so far 
constitute the smaller and critical 
dimension. Another main factor controlling 
height is that it must be lower than that 
allowing the wave to propagate in the other 
dimensions. Otherwise a guide is produced 
which is energised in this plane as well, i.e. 
a dual mode waveguide, sometimes used in 
practice. The height must also be kept 
reasonably high so that the waveguide thus 
formed can carry as much power as 
possible, as the breakdown occurs across 
the narrow dimension. Usually the ratio of 
the sides is 2:1, but a few are odd values up 
to 2.5:1 and various special non standard 
types are in the region of 4:1. 

In practice, therefore, a waveguide is 
specified for use over a frequency range of 
±2Q c 'c about a mean which is approximately 
1.5 times the cut off frequency. This keeps 
the operating point well away from the cut 
off, and also away from the region where a 
second mode could exist. Looking at Table 
II shows that in alternate sizes, one starts 
where the other leaves off. 

Various subscripts are added to indicate 
the form of wave in the tube. In the case 
considered, which as far as rectangular 
waveguide is concerned, is the one of real 
importance, if the tube is lying long side 
horizontal, say, and using the standard 
system of order of co-ordinates x, y, and z, 
the wave is referred to as TE10 (transverse 
electric, with one loop across the guide but 
with no loops vertical). 

If it were turned through 90° so the short 
side was horizontal, it would be a TEOl. But 
these are loosely used, however, to indicate 
the wave in question. This same process can 
be used to determine other modes of 
operation in tubes of various cross-sections. 

Thus, a method of transmitting energy 
through a hollow tube is practical — there 
are, of course, some problems in joining up 
the bits and pieces, and in making at¬ 
tenuators, loads and other components so 
that all the energy is still contained in the 
tube, and is properly terminated. 

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ELECTRONICS Australia, June, 1972 


59 












FORUM 

Conducted by Neville Williams 


When your hair has turned to silver . . . 


However diverse humans may be in other respects, we have one thing in 
common — we are all growing older, and the ramifications of this are not 
always pleasant to contemplate. It may even interfere with our enjoyment of 
music and music reproduction! 



The theme is introduced, this month, by a 
reader from Kingston Beach, Tasmania. He 
writes: 

Dear Sir, 

I would like to draw your attention to a 
problem, which I would assume that I share 
with many other readers of your magazine. I 
refer to the fact that our hearing curve drops 
a way at the treble end as our age goes up. 

I am 44, and it was recently found that my 
hearing is suffering in this way — something 
that I am assured is normal. 

Indeed, by cupping my hands behind my 
ears, an instant improvement is noticed in the 
higher frequencies. I would be pleased if your 
magazine could devote an article to this, on 
some occasion. 

What can be done within reason to diminish 
the problem when listening to hi-fi? A small 
tweeter closer to the ear than the main 
loudspeaker? It isn't only volume but direc¬ 
tion. 

Another matter on which I would like to see 
an article is the importance of absorbent 
packing in the loudspeaker enclosure and to 
what extent an improvement can be expected. 
My experiences tend to suggest that packing is 
undesirable but my faulty ears my be the cause 
of a wrong impression. 

F.B. (Kingston Beach, Tas) 

Unfortunately, the problem which F.B. 
speaks about is all too familiar to those of us 
who are on the wrong side of 35. It is a 
frustrating experience to be present in the 
lab when a younger person is observing the 
behaviour of a tweeter loudspeaker. The 
frequency goes up and up, then suddenly 
there is silence. Either the test is finished or 
the tweeter response has suddenly cut off. 

But no. The test is still going on and so is 
the tweeter. What has cut off is the response 
of “maturing” ears! - 

If you walk over and turn up the gain in an 
effort to reassure yourself, the other oc¬ 
cupants of the lab are likely to yell for 
mercy. 

Occasionally, the local medico may be 
able to recover a few odd decibels by de¬ 
waxing the outer ear but, in general, what is 
gone is gone and there is precious little one 
can do about it. 

In most cases, the loss is progressive and 
gradual and is largely unnoticed in the 
ordinary pattern of living. Virtually all the 
melody and all the fundamental tones of 


music are in the frequency range below 
about 5kHz, so that impairment of the upper 
frequency response does not prevent a 
person being involved with music in the 
ordinary way. 

They may or may not notice that in¬ 
struments seem to sound a little more 
“mellow” than once they did. 

People most likely to be aware of a 
hearing limitation are the high fidelity 
enthusiasts who, in one way or another, gain 
access to an audio generator. They feed its 
output into an amplifier and loudspeaker, 
run up the range and promptly start 
worrying about something that, previously, 
they were hardly aware of! 

Our correspondent asks whether there is 
anything he can do about it. 

Frankly, I’m not very optimistic. 

Without having researched the position, I 
have the broad impression that our sense of 
hearing exhibits a fairly sharp cut-off. 
Acuity may diminish gradually as the 
frequency goes up but there seems to be a 
region where it cuts off quite sharply. Many 
times I have seen people give answers “yes 
I do hear it” or “no I don’t”, when rocking 
the audio generator dial through a couple of 
kHz. 

Regarded as a low-pass filter, this is a 
very sharp cut-off indeed — far sharper 
than one would normally encounter in an 
electrical crossover network. It would be 
quite difficult to doctor the output of a 
reproducing system to produce the inverse 
of such a curve, even assuming that it would 
be worth attempting. 

But what about likely imbalance between 
a person’s two ears? And what about other 
people in the room, who may well be ex¬ 
posed to what would be, to them, a sharp 
peak in the treble response? 

Specially doctored headphones or 
headphone circuits might overcome some of 
the problems of imbalance and annoyance 
to others but not everyone would be 
prepared to forego the natural spaciousness 
of loudspeaker listening for headphones. 

The most practical approach may well be 
to take what advantage one can of the treble 
boost facility in the amplifier system, 
consistent with what other people in the 
home will tolerate. It will brighten up that 
part of the spectrum where useful response 
remains but it won’t do much to help above 
the cut-off frequency. 

However, I wouldn’t want this to be a final 


word on the subject. Our correspondent has 
highlighted a very real problem about 
which few will need convicing. Among our 
readership there may be those who have 
looked closely at it, with a view to evolving a 
practical answer. 

On the other matter raised by F.B. there 
are various reasons for suggesting the use 
of absorbent filling in loudspeaker en¬ 
closures. However, they do not add up to a 
case for always using filling. 

One approach to the design of compact 
loudspeaker systems is to mount a small, 
high compliance driver (typically of 6in or 
8in diameter) in a sealed enclosure no 
larger than it strictly needs to be. 

Such a system normally exhibits a bass 
resonance more prominent and at a higher 
frequency than that exhibited by the 
loudspeaker itself in free air. It may well be 
that the particular combination of loud¬ 
speaker and enclosure volume produces a 
bass resonance sufficiently prominent and 
sufficiently high in the range to give the 
bass an obvious “thumpy” sound. 

Filling the enclosure with a light texture 
acoustic wadding will usually reduce both 
the amplitude and the frequency of 
resonance, and minimise its effect on the 
general balance of the reproduced sound. 

Again, over the years, numerous vented 
loudspeaker systems have been con¬ 
structed by enthusiasts, using a variety of 
loudspeakers and a variety of enclosure 
designs. In some cases, the bass has been 
prominent enough but quite lumpy, due to 
peaks and troughs in the response curve. 

We have suggested that the lumpiness can 
often be smoothed out by partially filling or 
completely filling the enclosure with the 
lightest obtainable acoustic wadding. 

A further possible advantage of filling is 
that it inhibits standing waves in the en¬ 
closure at middle frequencies related to the 
internal dimensions. Sound waves which 
are generated in the box and emerge though 
the port or loudspeaker opening have been 
described as “honking”. 

If an unfilled loudspeaker system does not 
exhibit a prominent bass resonance, or a 
lumpy bass characteristic, and if the in¬ 
ternal faces are padded sufficiently to stop 
mid-range reflections, there is no point 
whatever in filling the interior with acoustic 
wadding. 

On the other hand, a designer committed 
to a certain loudspeaker and a certain 
enclosure size may elect to use acoustic 
filling as a deliberate part of the design. In 
such a case it would almost certainly be 
wrong to take it out. 

In general terms, the use of acoustic 
filling will tend to reduce loudness, par¬ 
ticularly at the bass end. Therefore, judged 
on the basis of the amount of noise a system 
can make at low frequencies, filling would 
always be rejected. However, if the filling 
produces a smoothly tapering bass 
response, and if this tapering response can 
be compensated easily with bass boost from 
the amplifier, the end result may be much 
more pleasant and natural. 

So much for audio / hifi. 

If you’re in the mood for a chuckle have a 
look at the letters and the illustration at the 
top of the next page. The best chuckle, 
however, came in a quite unexpected way 
when the letter from J. I. came to the notice 
to a visitor to our office who does not have 
the advantage of having been born in 
Australia! 


60 ELECTRONICS Australia, June, 1972 





A 





He chortled at the contents and then 
laughed uproariously at the very ap¬ 
propriate “fake” address. What a 
humourist J.I. must be. 

We had to resort to the postcode book to 
convince him that there was, in fact, such a 
place as Upper Ferntree Gully! 

Back to more serious matters, attention 
has been drawn from time to time to the fact 
that, superficially, the Australian Broad¬ 
cast Listener’s Licence confers on the 
listener only the right to listen to broadcast 
stations, and in particular to those on the 
medium-wave broadcast band. 

There is a 50 / 50 chance that the 
receivers which he is able to buy without 
hint of restriction contain provision for 
receiving a whole array of signals spread 
over the high frequency bands. Very few of 
the HF transmitters carry Australian 
broadcast programs. The vast majority are 
overseas broadcasters, amateur stations, 
communication services and so on. 

A Broadcast Listener’s Licence does not 
specifically cover the right to listen on these 
or other frequencies. But, equally, no other 
licence exists which does. We are left in the 
rather odd position where, provided we hold 
a Broadcast Listener’s Licence, we can 


16 million television licences goes to the 
BBC. It is, therefore, no longer a licence fee 
but a program charge. 

“Readers may well ask why we should 
now be getting steamed up about something 
which has been going on for a very long 
time. Quite unwittingly we have, ap¬ 
parently, been inciting readers to break the 
law. Little did we think when we published 
the recent articles on the reception of 
weather maps from satellites that a special 
receiving licence would be required by 
those who made and operated the equip¬ 
ment described. 

“We are told by the Ministry of Posts and 
Telecommunications, although we have so 
far not received this in writing, that it is 
illegal to receive transmissions from a 
satellite. Apparently, a television licence — 
the only receiving licence now generally 
available to the public — permits, as did the 
sound licence, reception of “authorised 
broadcasting stations . . . and licensed 
amateur stations’’ and a satellite is not, we 
are told, a broadcasting station! 

“A similar situation exists, of course, 
regarding the reception of aircraft VHF 
transmissions and those in the marine radio 
band. For although receivers covering 
these bands are available to the public it is 
illegal to use them. 

“As a journal, we have always main- 

- tained the need for law and order in the 

enjoy a purely de facto right to listen to transmission and reception of ‘elec- 
any thing else which we may happen to tune tromagnetic waves although from time to 
in on a tuneable multi-band receiver. time we ^ ave been critical of the ad- 

The Wireless Telegraphy Act does, ministration Could we not have one 
however, impose a now somewhat dated receiving licence covering all types of 
condition that we must not communicate to transmission 0 

a third party, or otherwise take unfair 
advantage of any private message that we 
might intercept. 

This leads naturally to a couple of very 
pertinent questions: (1) Why do people need 
to pay a licence merely to operate a 
receiver, as distinct from a fee to support a 
broadcasting system? (2) If messages are 
private or confidential why are they trans¬ 
mitted in a form that can be understood by 
a casual listener? 

It is interesting to note that we are not 
alone in this dilemma. It is relevant to quote 
from the editorial in the January issue of 

our associated English Journal “Wireless o , D ■ 

Wsx«.isi” if __ lt i j Manufacture of Printed Circuit Boards 

World In spirit it could have been written , or the , ndustry and Hobbyists. 

in ^Australia for Australia. E. A. Project Boards also in stock. 

. . . Now, except for a collecting fee a e DQiuTrn ciociiitc 
claimed by the Post Office, and expenses vl-F, r P !/ nI E ? c C RC u 7 S , 
incurred in the investigation of in- 52 Union Road. Surrey Hills. Vic. 3127. 

terference, the whole of the income from the 4 7bl " 


THOSE 

SUPPORT 

BRACKETS 


Dear Sir, 

The article on page 71 of the April issue 
relating to the Trichotometric Indicator 
Support Bracket was of considerable interest, 
as for some time problems have been experi¬ 
enced with the Trichotometric Indicator 
supports fitted to machines used in the manu¬ 
facture and packaging of adjustable set- 
spanners, striped paint and prefabricated 
sparks suitable for automotive ignition 
systems. 

By making up the bracket in accordance 
with the detail, the problems have now been 
overcome, and I am now able to commence 
production of ambihelical hex nuts of the type 
used to secure the support. 

J. I. (Upper Ferntree Gully, Vic). 

Dear Sir, 

In your April issue you showed a diagram of 
a Trichotometric Support Bracket, locked in 
place with a special Ambihelical Hex nut. By 
sheer coincidence a recent cartoon in the 
Sydney ' Sun” contained a sketch of the 
factory in which both these items are made. 

G.W. (Jannali, NSW). 



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ELECTRONICS Australia, June, 1972 


61 





































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ELECTRONICS Australia, June, 1972 


1213 ) 478-0095 


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70 BATESFORD ROAD, CHADSTONE, 
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1 

BOOKS & 

1 

_ 

LITERATURE 

J 


Network theory 

ASPECTS OF NETWORK AND SYSTEM 
THEORY, edited by R. E. Kalman and 
N. DeClaris Published by Holt, Rinehart 
and Winston, Inc, San Francisco, 1971. 
Hard covers, 235mm x 155mm (6in x 
9>/4in), 648pp. Price in Australia $19.95. 

Despite its unlikely title, this book is 
really a memorial. It is a collection of 
papers dedicated to the memory of 
Professor E. A. Guillemin, professor of 
electrical engineering at Massachusetts 
Institute of Technology from 1944 to 1963, 
and author of classic texts in circuit and 
network theory. Professor Guillemin died 
on April 6, 1970 at the age of 72. He had 
written some seven textbooks and 37 
papers, and could claim a long list of in¬ 
ventions — including the “Guillemin line” 
developed during the second world war for 
the generation of radar pulses. 

The papers which form the book are all 
quite deep, and are intended mainly for 
engineers, research workers and 
academics. They are divided into five main 
sections, headed: 1 — Analysis; 2 — Syn¬ 
thesis; 3 — Generalisations; 4 — Ap¬ 


LARGEST RANGE IN 
AUSTRALIA OF 
ELECTRONIC 
AND RADIO BOOKS 

Mail order available, prompt attention. 
See below for this month's new 
publications. 

Colour Television with Reference 
to P A 1. System by Patchett $7.50 

Hi-Fi Year Book 1972 $4.00 

Radio Valve and Transistor Data by 
(A.R.R.U 1972 $6.95 

Radio Valve and Transistor Data by 
Ball $2.65 

Amateur Radio Techniques by Pat 

Hawker (R.S.G.B.) $3.90 

Audio Cyclopedia by Tremaine $30.00 

A.V.O.Valve Data Manual $12.50 

Transistor Audio Amplifiers by 
Tharma lliffe $19.00 

Transistor Pocket Book by Hib- 
berd . $4.25 

Add 50c for postage 

McGILLS 

Authorised Newsagency Pty. Ltd., 

187 Elizabeth Street 
MELBOURNE VIC. 3000 Phone60 1475 


plications; 5 — Pedagogical. There are 28 
papers in all., The book begins with a 
memorial to Professor Guillemin, and ends 
with author and subject indices. 

The review copy came from Holt, 
Rinehart and Winston (Aust.) Pty Ltd. 
Copies should be available at all major 
bookstores. (J.R.) 


Electrical experiments 

NOVEL EXPERIMENTS WITH ELEC- 
TRICITY, by John Potter Shields. 
Published by W. Foulsham & Co Ltd, 
Slough, Bucks, England, 1971. Hard 
covers, 5V 2 in x 8 3 / 4 in (140mm x 220mm), 
96pp, many diagrams. Price in Aus¬ 
tralia, $4.25. 

The aim of this book is to help the reader 
learn the basic facts about electricity and 
magnetism without the aid of complex and 
expensive apparatus. It includes ex¬ 
periments which range from a simple 
electroscope to a synchronous motor, from 
simple magnets to a model spark coil. Many 
of the parts should be available from a junk 
box; other parts should be readily available 
through electronic supply stores. 

There are only four chapters: Basics of 
Electricity and Magnetism; Basic Ex¬ 
periments in Electricity; Experiments with 
Magnetism; Miscellaneous Electrical 
Experiments. In addition there is a chapter 
for the English reader explaining the dif¬ 
ferences between conditions in the USA 
(where the book was written) and in the UK. 
The chapter points out that the difference 
between the US mains and the British mains 
supplies is such that many of the ex¬ 
periments are dangerous and should be 
carried out only under adequate super¬ 
vision. A similar comment would apply for 
Australia. 

The book provides an interesting selection 
of experiments which should be of 
assistance to any beginner, provided that 
adequate safety precautions are taken when 
working with live mains. Even with that 
proviso, however, some of the experiments 
would be best omitted where the higher 
mains supply voltage makes them ex¬ 
cessively dangerous. 

The review copy was supplied by Gren¬ 
ville Publishing Co Pty Ltd, 401 Pitt Street, 
Sydney. Copies should be available from 
most larger booksellers. (J.H.) 

Test instruments 

RADIO, TELEVISION AND AUDIO TEST 
INSTRUMENTS, 2nd Edition, by Gordon 
J. King. Published by Newnes- 
Butterworths, London, 1972. Hard 
covers, 160 x 255mm, 199pp, many 
illustrations. Price in Australia $12.70. 

The second and revised edition of another 
book originally written for Odhams Press 
by well-known British technical author 


Gordon King. It is a companion volume to 
his other books on servicing, such as 
“Television Servicing Handbook” and 
“Colour Television Servicing”, which were 
reviewed recently in these columns. In fact 
it supplies some of the information on 
practical servicing and the actual use of 
instruments that I would have liked to have 
seen in these volumes. 

The present book is a basic introduction to 
the measuring instruments used in ser¬ 
vicing, as the title suggests. The contents 
and their order of presentation are shown 
fairly clearly by the chapter headings: 1— 
An Introduction to Instruments; 2— Ap¬ 
plication of DC Meters; 3— Application of 
AC Meters; 4— Electronic Meters; 5— 
Signal Generators; 6— The Oscilloscope; 

7— Some Applications of the Oscilloscope; 

8— Valve, Picture Tube and Transistor 
Testing; 9— Miscellaneous Instruments; 
10— Instruments for Colour Television; 11- 
Instruments for Audio. 

To me the book seems to be clearly 
written, and well presented — although 
there are one or two annoying publishing 
errors such as the transposition of a block in 
chapter 4 with another in chapter 11 (Figs 
4.6 and 11.6). It should be found of con¬ 
siderable value by service technicians and 
trainees, students and enthusiasts. 

The review copy came from Butterworth 
and Co (Aust) Ltd, who advise that copies 
should be obtainable at all major 
bookstores. (J.R.) 

LITERATURE — in brief 

FAIRCHILD AUSTRALIA PTY LTD. PO Box 151, 
Croydon, Vic 3136, has published a comprehensive data 
sheet for Fairchild zener diodes, covering the series 
AN753-759and AN962-973. Utilising the planar process, 
these silicon diodes feature a voltage range from 6.2 to 
33V, ultra-stable reverse voltage, low leakage, low 
dynamic impedance, and high reliability. 

HEWLETT-PACKARD JOURNAL, Vol 23, No 5, 
January, 1972. Published by the Hewlett-Packard Co, 
USA. Contents: A computer-aided hospital system for 
cardiac catheterisation procedures; Clip-and-read 
comparator finds IC failures; The well-modulated 
synthesiser. Inquiries to Hewlett-Packard Aust Pty 
Ltd, 22-26 Weir Street, Glen Iris, Vic 3146. 

PLESSEY DUCON PTY LTD, PO Box 2, Villawood, 
NSW 2163, has published a four-page product data 
sheet, PD 2076, which gives detailed technical in¬ 
formation concerning an E-cell marketed by the 
company’s Professional Components Department. The 
E-cell is a reversible electronic integrator with non¬ 
volatile memory for timing, integrating and counting. 
A brief description of the device is accompanied by 
diagrams showing its construction, its equivalent 
circuit, and a typical operating curve. Full charac¬ 
teristics of the device are presented numerically and 
graphically. & 


ALL BOOKS 

REVIEWED IN THESE 
PAGES 

(AND HUNDREDS OF OTHERS) 
AVAILABLE FROM 

TECHNICAL BOOK CO. 

289-299 SWANSTON STREET, 
MELB. 3000. Ph. 663-3951 


ELECTRONICS Australia, June, 1972 


63 








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ELECTRONICS Australia, June, 1972 


lOOl 









CIRCUIT & DESIGN IDEAS 


Interesting circuit ideas and design notes selected by the Editor from technical literature, reader contributions 
and staff jottings. As they have not necessarily been tested in our laboratory, responsibility cannot be 
accepted. Contributions to this section are always welcome. 



A Simple Short Wave Converter 


Opposed to the trend towards more 
complexity in circuits, the simple converter 
shown here may be used with a portable 
transistor radio to pick up short wave 
signals. The radio set provides the IF and 
audio amplifiers and any crystal which is 
either 455KHz higher or lower than the 
wanted frequency should be suitable. 

In operation, the signals are picked up by 
the aerial and coupled to the tuned circuit 
L1-C2. The inductor consists of 13 turns of 
22B&S enamel wire wound on a 1 a in 
diameter, 1-3 16in long ferrite core and 
tapped 4 turns up from the ground end. 
Capacitor C3 connects to Ll at the best point 
for impedance matching. The signal is 



amplified by Ql and mixed with the 
frequency generated by the crystal to 
produce an IF which is either the sum or 
difference of the two. This is passed on to 


the receiver IF input. 

Any one of several types of transistors 
may be used for Ql, provided it is of the high 
frequency type. 

To use the converter, hook up an outdoor 
aerial about 20 feet long. Turn on the power 
and start with C2 fully meshed. Slowly 
decrease C2 until short wave signals are 
heard. As the frequency of the crystal is 
reached, the converter will go dead and 
then come on again as the frequency is 
passed. The crystal will beat with signals 
first on the low side and then as C2 is tuned 
further, signals on the high side will be 
heard. 

(By Larry Lisle, in “Popular Elec¬ 
tronics”.) 


Diode Probe Electronic Thermometer 


A silicon diode probe and an operational 
amplifier with an unusual gain adjustment 
are the key elements in an electronic 
thermometer that gives a readout, in 
degrees, on an ordinary voltmeter. The 
sensing circuit’s voltage variations can be 
adjusted to align with a temperature scale. 
For instance, a 10- or 100- millivolt reading 
can represent 1°C at one setting or 1°F at 
another setting of the amplifier. 

The operational amplifier is connected as 
a differential-amplifier. An input that varies 
with the temperature of probe D1 is ob¬ 
tained through resistor Ftl and part of R2. 
Zener diode D2 and R3 provide a reference 
voltage; offset is adjusted by R4. R2 is the 
gain adjustment, but it is not entirely within 
the feedback path as shown on the diagram 
of the conventional differential amplifier. In 
the location used, R2 helps to make the 
output both linear and scalable. 

After potentiometer R2 in the actual 
circuit is adjusted to bring the output within 
a suitable range on the voltmeter, poten¬ 
tiometer R4 is used to adjust offset. This 
aligns V out with the desired temperature 


+ 15V 



scale so that the reading corresponds to 
degrees without further conversion. The 
instrument is calibrated by setting R4 with 
the probe at a known temperature. 

Metal film resistors, wire wound 
potentiometers, and the small temperature 
coefficient of the temperature compensated 
zener diode give the circuit excellent 


temperature stability. Minor variations in 
supply voltage do not significantly affect 
accuracy. Since the dynamic impedances of 
the two silicon diodes are matched closely, 
supply voltage changes result in a common¬ 
mode input signal that is greatly attenuated 
by the amplifier. 

(By Robert J. Battes, in “Electronics”.) 


Silicon Diode Sweep Generator 


This simple RF sweep generator has 
proved invaluable for aligning IF and RF 
circuits over a wide range of frequencies. 
The circuit consists of a Colpitts oscillator 
which is swept by means of two varactor 
diodes. The diodes are direct coupled from a 
unijunction sawtooth oscillator, via a 
common emitter stage. The sawtooth is also 
used for the CRO horizontal sweep. 

The RF oscillator uses plug-in coils 
enabling any desired centre frequency to be 


selected. The greatest frequency sweep will 
occur when the capacitance of the tuned 
circuit is kept to a minimum, which means 
that a typical 455KHz IF coil needs extra 
turns added for best results. A 50KHz sweep 
has been obtained at 455KHz and the circuit 
has been tested uo to 10.8MHz. 

To prevent the diodes from conducting at 
any point of the RF cycle when maximum 
sweep width is used, the oscillator level is 
kept low by means of the 10K dropping 


resistor. Correct operation may be checked 
by displaying the RF output on a CRO. If the 
level drops at the low frequency end of the 
sweep, the 10K resistor should be increased. 
However, the stage may fail to oscillate if 
the voltage is reduced too much. Any 
germanium PNP RF transistor should be 
satisfactory for the RF oscillator. 

The .unijunction oscillator and the 
following stage are so arranged to produce 
a sawtooth waveform with some curvature. 


ELECTRONICS Australia, June, 1972 


65 































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51*2 lb. 

115 

TS115 2000A 

2000 

17.4 

8*4 

8*4 

79 lb. 

SOLDERING IRON TRANSFORMERS — Enclosed in pressed steel cover 
Mico or Oryx Soldering Irons 

— suitable for 

5 . 6 . 7 . 

TS7 20 

20 

2.85 

33/8 


23/4 

2*2 

10,11,12, TS12 40 

40 

3.33 

3% 

2*8 

3*4 

3*2 


All transformers in this range are suitable 
for connecting to a 240 volts, 50 cycles, 
single phase supply and, where applicable, 
comply with Australian Standard C126 
1950 under approved Number N158. 

FUSEMASTER RANGE:— 

All transformers housed in steel cases ("A" 
and "B") fall into the above category. 

A TYPE 

• Fuse protection of output. 

• Three core primary flex 6’6” long. > 

• Conduit or grommet knockouts. 

• Primary and secondary terminal blocks. 

• Carrying handle. 

t Provision for wall mounting. 

BTYPE 

• Fuse protection of output. 

• Three core primary flex 6’6” long. 

• Carrying handle. 

• Provision for wall mounting. 


Available from recognised electrical wholesalers 

FERGUSON TRANSFORMERS PTY. LTD 

331 HIGH STREET, CHATSWOOD, N.S.W. • P.O. BOX 301, CHATSWOOD, 2067. 
TELEPHONE 40-0261 (8 LINES) • TELEGRAMS: "FERTRAN." 


66 


ELECTRONICS Australia, June, 1972 





















CIRCUIT & DESIGN IDEAS 



Signal Injector Uses 1C 

After reading about “A Useful Signal 
Injector” in Circuit & Design Ideas for 
February, 1972, I found that the transistor 
type AS28 was difficult to obtain. As a 
result, I decided to make up an injector 
using a Motorola IC type MC799 / P and the 
circuit shows what I came up with. It is 
basically a battery powered 1000 Hz 
multivibrator that generates square waves. 
The amplitude of the square wave output is 
fully variable and sufficient to test a 
loudspeaker. 

The injector also provides a wide band¬ 
width RF signal suitable for testing RF and 
IF stages. Current drain is of the order of 
80mA which allows of a reasonably long 
battery life. The resistors used were V 4 W 
types and the IK potentiometer is a carbon 
type, with switch. The two O.luF capacitors 
are 10V disc type, the lOOpF capacitor is 


Bert Allen, G 2 UJ, points out that there is 
a simple way of adding contacts to existing 
relays. This is done by employing the 
existing energising coil to operate one or 
more reed switches, in addition to the 
normal spring set. 

All that is necessary is to fix one or more 
of these reed switches on the outside of the 
relay coil, parallel to the coil. They can be 
fixed in position using adhesive tape. 

G 2 UJ gives as an example that a 100 ohm 
relay coil operating at 6 V will actuate as 
many reed switches as can be placed 
around the outside of the centre of the coil, 
other than close to the framework. And all 
this, it should be noted, without interfering 
in any way with the normal operation of the 
relay. 

There may also be some readers who do 
not realise that these little reed switches 
can readily be actuated by the physical 
movement of a small magnet. This ap¬ 
proach has in the past been used in such 
applications as burglar alarms, for in¬ 
terlock systems, etc. The only difficulty 
with some of these applications is that if a 



This tends to counteract the non-linear 
capacitance voltage characteristic of the 
diodes. 

The 25K trimpot should be set so that the 
stage just bottoms (saturates) at the 
beginning of the sweep. If saturation cannot 
be obtained with the trimpot set to 
maximum, reduce the value of the 1 M base 
feed resistor. 

The sweep width control is very useful 
when checking amplifiers using narrow 
band ceramic, crystal, mechanical or LC 
filters. Under these conditions, only a few 
sweeps per second are used to prevent 
ringing effects. Also, the display may be 
expanded to show a vei*y small part of the 
spectrum in detail. 

The original unit was assembled on a 3in 
strip of tag board and mounted with the 
battery, controls and sockets in a 4in x 4in x 
2 in box. Several suitable coils with tuning 
slugs were salvaged from an old all-band 
receiver. 

(By Mr P. H. Mathieson. M.I.E. Aust., 
Box 67, Ukarumpa. E.H.D., PNG.) 


also a disc type. 

Construction may be left to the individual 
ideas and requirements of the builder. 
Many ideas will no doubt suggest them¬ 
selves, possibly dictated by what materials 
and facilities happen to be available at the 
time. 

(By Mr N. Hodgson, 3 John Street, 
Frankston, Victoria 3199.) 


JEMCO 

HIGH SENSITIVITY 



us-105 MULTIMETER 

UNBEATABLE FOR VERSATILITY , 
ACCURACY , RELIABILITY , VALUE 

• 50/000 Ohms / Volt. 

• Double overload protection. 

• Polarity reversing switch. 

• 10 amp AC & DC ranges. 

• Resistance to 200M. 

RANGES 

DC V 0.25/ 1/ 2.5/ 10/ 50/ 250/ 1000 
AC V 2.5/ 10/ 50/ 250/ 100 
DC A 50uA, 1/ 25 / 500mA, 10A 
AC A 10A 

Ohms Rxl/ xlO/ xl00/ xlK/ xlOK 
Size: 5Ve" x 4'/e" x 1 Ve" 

Price: S36.20 incl. S.T. 

also: Popular US-100 model 

20,000 0/ V $31.50. 

Warranted 3 months—Repair Service. 

Available ex stock from leading merchants or sole 
Australian distributors: 

INDEVA PTY. LTD. 

24 BELLEVUE ROAD, 

BELLEVUE HILL. 2023 

_ T»l.: Sydnty 36 4401 _ 


Applications for Relay Reeds 

reed is held closed over a very long period 
there is always some slight danger that a 
cold weld may cause the contacts to stick 
and remain closed. 

On this general subject of using reed 
contacts, Peter Chadwick, G3RZP, draws 
attention to the important limitation when 
used for switching RF due to skin- 
resistance effects. He considers that when 
used, for example, in aerial change-over 
applications the real limitation is in the 
power handling. His own experiences 
suggest that about 1.7A of two-tone SSB 
represents the practical limit, although on 
speech transmission it may be possible to 
push the level a little higher. It is important 
to appreciate that this limit stems from the 
effect of skin resistance — a point which we 
underlined back in 1966 following 
discussions in Stuttgart with Heinz Rensch, 
the reed relay expert of SEL. 

Even with heavy gold plating, G3RZP 
finds the reed can get so hot that the 
material either passes its Curie tem¬ 
perature or the glass distorts. 

(From ‘‘Radio Communication”.) 

ELECTRONICS Australia, June, 1972 67 































































Workofart6EA8 


Craftsmanship in metal and glass. 

The AWV 6EA8 oscillator/mixer valve: 
eyes and ears of the television receiver. 

A work of electronic artistry created 
to pluck a television signal out of the air, 
designed to receive both audio and video 
signals, and constructed with the technical 


perfection of all true works of art. 

An example of the special beauty 
that AWV sees in both the function and 
design of electronics. 

An object no less beautiful because 
of its everyday application. 

For AWV, electronics is a living art. 



Amalgamated Wireless Valve Co. Pty. Ltd., your experts in the art of electronics. 


ELECTRONICS Australia, June, 1972 



HOME STUDY COURSE IN ELECTRONICS — 14 


Power Supplies 


Valve equipment power supplies — problems in using AC to heat valves — 
the indirectly heated valve — the full-wave rectifier, using valve diodes — 
smoothing and filtering with inductance and capacitance — the use of 
semiconductor diodes — the voltage-doubler rectifier — the half-wave recti¬ 
fier — transistor equipment power supplies — the bridge rectifier — 
dynamic filtering and regulation. 


For the sake of simplicity, most of our 
circuit discussion to date has assumed the 
provision of suitable DC supply voltages, 
without much emphasis on how such 
voltages are obtained. In this chapter, we 
explain how supply voltages are derived 
from the AC power mains. 

In the early days of radio, receivers were 
invariably supplied from batteries. It was 
commonplace to use either an accumulator 
for the filament supply or a number of 
heavy-duty dry cells capable of supplying 
the requisite and often considerable 
filament current. 

The grid bias voltages were taken from a 
special bias battery, not intended to deliver 
significant current, but with tappings at 
each cell junction to give voltages in lV 2 -volt 
steps to 4V 2 volts or 9 volts — to quote what 
were common figures 

For the plate supply, so-called radio “El¬ 
ba tteries” were used. These were large and 
rather expensive banks of dry cells, usually 
made up in 45-volt blocks and tapped at 22 V 2 
volts. Two such B-batteries in series could 
supply 90 volts, while three in series were 
commonly employed to give 135 volts. How 
cumbersome and expensive these batteries 
were tends to be forgotten in these days of 
transistor receivers. 

While the early sets were simple enough 
from the designers’ point of view, the need 
to provide, attach, and conserve batteries 
was a constant worry to radio set users and 
it was natural that efforts should be made to 
cut the operating costs, at least. As a result, 
various gadgets appeared aimed at supple¬ 
menting or replacing the expensive bat¬ 
teries. 

Numerous chargers or “trickle chargers” 
were put on the market for recharging the 
filament accumulators. The chargers might 
deliver currents up to 3-odd amperes and 
would top up a discharged battery in a day 
or so. Trickle chargers were designed to be 
left on more or less continuously, keeping 
the battery full at air times and saving the 
hitherto regular trip to the local garage for 
a battery re-charge. 

So-called “B-Battery Eliminators” were 
released, to replace the high-tension bat¬ 
teries altogether. These incorporated a 
transformer, rectifier and filter system, 
rather like a modern AC power supply. 
Various resistors and tapping points were 
included so that they could supply the 
requisite intermediate voltages at the order 
of current drain commonly encountered in 
battery sets of the day. 

Some B-battery eliminators also included 
auxiliary circuits to provide negative bias 


voltages, although the cost of a bias battery 
was never a major item. 

These various units enjoyed a limited de¬ 
gree of popularity, but the obvious objec¬ 
tion of having gadgets and accumulators 
attached to the family radio provided strong 
incentive to produce self-contained receiv¬ 
ers which could simply be plugged into the 
power point and operated therefrom just 
like any other electrical appliance. 

Initially, the main difficulty was that of 
providing filament supply. For reasons we 
shall see a little later, AC from the power 
mains could not readily be changed to DC at 
the voltage and current needed to operate a 
number of parallel-connected filaments. 
And there were — and still are — two basic 
objections to applying AC to the filament of 


variation in the number of electrons 
produced, and thus still tends to modulate 
the plate current to produce an undesirable 
hum (in this case at twice the AC supply 
frequency). In an attempt to overcome this 
problem the directly heated valves used in 
early AC receivers had special low-voltage 
high-current filaments made from thick 
wire and therefore thermally sluggish. 
However this was only partly successful. 

A satisfactory solution to the problem 
only came with the introduction of valves 
having “indirectly heated” cathodes. Such 
valves were described in an earlier chapter. 

With the development and release of 
valves having indirectly heated cathodes the 
major problem with all-mains operation 
disappeared and numerous receivers were 
released using them. It was still necessary 
to produce from the mains a pure DC supply 
for the valve plates and screens, but, as we 
shall see, this was not — and is not — a 
major problem. 

In most radio receivers, amplifiers and 
other equipment using valves, the DC 
supply for the plates and screens is 


FILTER 

CHOKE 


HT 

SECONDARY 

WINDING 



Figure 1: A typical power supply circuit using a valve rectifier as used in older 
receivers and amplifiers. Supplies using semiconductor rectifiers are more common in 
modern receivers. 


a directly-heated valve. 

The first and perhaps most obvious ob¬ 
jection is that because the filament has a 
certain voltage drop, the effective bias 
between filament and grid varies over its 
length. As a result if the filament is heated 
by the application of AC, an alternating 
voltage component tends to be super¬ 
imposed upon the desired DC bias to 
modulate the plate current and cause hum. 
It is possible to cancel out most of this 
superimposed component by accurately 
centre-tapping the filament AC supply, and 
this was done with early receivers designed 
to be operated directly from the mains. But 
unfortunately this technique does not avoid 
the second problem. 

Because alternating current falls to zero 
twice in every cycle, the temperature of the 
filament tends to vary cyclically when AC is 
used to heat it. This causes a corresponding 


provided by a power supply circuit using 
a transformer and rectifier. In early 
equipment the rectifier used was a valve, 
usually a double diode. In more modern 
equipment silicon diodes are used. 

Figure 1 shows a typical valve rectifier 
power supply circuit, whose operation we 
can proceed to discuss. 

The heart of the supply is the power trans¬ 
former, which is shown diagramatically as 
a number of windings adjacent to an iron 
core. The transformer is used to provide 
low voltage AC for the valve heaters as well 
as the plate supply. 

The incoming power lead is connected 
across the primary winding, which will 
normally be rated to receive an input of 240 
volts AC. It must be AC. A power trans¬ 
former must not be connected across DC 
mains. If it is, it is almost certain to blow 
the fuses or burn itself up, or do both! 


ELECTRONICS Australia, June, 1972 


69 




















NOYES BROS. PTY. LIMITE 


hawker sodeley comrwmy 


KT CONTACTORS 

comply with Australian Standard 
C 63 — 1965 and British Stan¬ 
dard 775: 1969. This new range 
is designed for use where 
economy, reliability and com¬ 
pactness are paramount. 
Publication 11000. 


THERMAL 
OVERLOAD RELAY 

with ambient temperature com¬ 
pensation and single phasing 
protection provides one of the 
most economical and effective 
methods of motor overload pro¬ 
tection. 

Publication No. 12100/12200. 


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Insulated metallic case for maximum thermal conductivity 
Diffused silicon junctions with avalanche characteristics 
Small size — simple installation 


The MINIBRIDGE was designed to replace larger 
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25A Type 
PIV/I 
8A Type 



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DISTRIBUTORS: 

Watkin Wynne Pty Ltd, 32 Falcon St, Crows Nest. Tel: 
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PB Components, Melbourne. Tel: 53 2766. 

Fairchild Aust Pty Ltd, Sydney. Tel: 439 4355. 

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GEC-Elliott Automation Pty Ltd, Sydney. Tel: 439 1922. 
GEC-Elliott Automation Pty Ltd, Adelaide. Tel: 71 7971. 


GEC-Elliott Automation Pty Ltd, Brisbane. Tel: 32 0441. 
GEC-Elliott Automation Pty Ltd, Melbourne. Tel: 387 2811. 
H. Rowe a Co Pty Ltd, Perth. Tel: 28 5444. 

The National Electrical & Engineering Co Ltd, Auckland. Tel: 
553 709. 

The National Electrical a Engineering Co Ltd, Auckland. Tel: 
599 089. 


70 ELECTRONICS Australia, June, 1972 











t- 


The reason for this is not hard to discover 
in that a transformer relies for its operation 
on a constantly changing magnetic field. As 
the alternating current from the power 
mains flows to and fro through the primary 
winding, it causes a strong magnetic field in 
the iron core to build up and collapse in 
cyclic fashion. The moving lines of force 
thus created induce current and voltage in 
the various secondary windings, obeying 
the laws of magnetism explained in an 
earlier chapter. 

The alternating voltage developed across 
each secondary winding is almost exactly 
proportional to the ratio of turns between 
the primary and the secondary winding in 
question. Thus, if there are 1,200 turns on 
the primary winding, a secondary winding 
also having 1,200 turns would deliver the 
same 240 volts as fed into the primary — 
because the turns ratio would be 1:1 On the 
other hand, if a 6.3 volt winding is required 
to operate a number of valves with 6.3 volt 
heaters, then this heater winding would 
need to have 1,200 times 6.3/240, or ap¬ 
proximately 32 turns. 

In the above illustration we suggested 
1,200 turns for a 240-volt winding on the 
assumption that the transformer might be 
wound on the basis of five turns for every 
volt of input or output. This is a likely 
enough figure, but, in practical trans¬ 
formers, the turns-per-volt figure may vary 
considerably from one type to another, 
according to the size of the core, the grade 
of the iron used and the ideas of the 
designer. 

The thickness of the wire used on each 
winding depends on the current which it has 
to handle or deliver. In the case of a heater 
winding, which may be required to deliver 
several amperes, relatively thick wire has 
to be used and it is commonplace to see 
heater windings using 16-gauge enamelled 
wire or thicker. 

It is important to realise that the gauge of 
wire used in a transformer winding 
determines only the amount of load current 
it can handle, without over-heating, if 
required to do so. Thus a winding rated to 
deliver, say, three amperes, can deliver up 
to three amperes without tending to 
overheat, according to the number of valves 
which may be connected to it. If only one 
valve were connected to the particular 
winding, the current drawn from it would 
probably be less than one amp. 

Typical low power transformers designed 
for use in the power supply of a radio set, 
television receiver or similar equipment 
may have one, two or even three heater 
windings, to give the voltages and currents 
likely to be required. If designed in recent 
years for valve equipment, most heater 
windings are likely to be designed to 
produce a voltage of-6.3 volts RMS, to suit 
most modern valves. 

In the circuit of figure 1 we have shown 
two heater (or filament) windings, one to 
supply the rectifier and the other to supply 
the heaters of all other valves in the 
receiver. The latter is shown as having a 
centre-tap connection, earthed to the 
chassis. 

Heater wiring is usually earthed for two 
reasons: 

Firstly, the heater winding is very close, 
inside the transformer, to other windings 
producing high alternating voltages. 
Because there is some capacitance between 
them, some of the high voltage energy can 







A typical transistorised regulated power 
supply suitable for use with experimental 
circuits. It provides an adjustable output 
voltage from 0 to 30V at a maximum 
current of 1 A. The meters are included to 
indicate the output current and voltage. 


List Nos.: B.3, B.2, B.l 
Three, Two and One 1035 Cell 
respectively 


List No. B.ll 

One 1015 Cell 


Ex-stock from Wholesalers 
or Australian Agents 


be coupled capacitively to the heater wind¬ 
ing and to the wiring connected to it. 

This doesn’t interfere in any way with the 
basic operation of the heater circuit but the 
high ripple voltage present on the heater 
wiring throughout the chassis can couple 
into grid circuits and produce an objection¬ 
able hum or buzz in the output. 

A second reason is that wiring running 
from one stage to another thoughout a high- 
gain receiver can transfer signals by stray 
coupling and produce troublesome 
regeneration. 

Earthing the heater wiring largely ob¬ 
viates both effects. Although we have shown 
a centre-tap earth return, this is not strictly 
necessary except, perhaps, in equipment 
having very high audio gain. In many cases 
it is sufficient to earth one side only of the 
heater wiring. 

For the plates and screens, AC from the 
power mains must be rectified and filtered 
till it becomes virtually pure DC. This in¬ 
volves, normally, a high tension secondary 
winding on the power transformer, a 
rectifier, a filter choke and two or more 
filter capacitors. 

As might be expected, the high tension 
winding involves many turns of fairly fine 
wire, so that a considerable voltage is 
developed between its outer ends. Since the 
voltage across it is alternating, each end 
swings alternately positive and negative 
with respect to the other. 

In valve rectifier circuits such as that 
shown, the high tension secondary winding 
has a centre-tap which is returned to 
chassis (shown as earth) so that half the 
total secondary voltage appears between 
earth and the respective ends. When one 
end of the winding swings positive with 
respect to earth the other end 
simultaneously swings negative by an equal 
amount. 

As with the heater windings, the rating of 

ELECTRONICS Australia, June, 1972 


ALWAYS 

use BULGIN 

Battery Holders 


List No. B.7 One 
1.035 Cell 


List No. B.10 

One 1050 or 
or 1035 Cell 


PT V. LTD. 

VIC.: Cnr. Dryburgh & Victoria 
Sts., West Melbourne. 
329-9633 

N.S.W.: 64 Alfred St., Milsons 

Point 2061. 929-8066 

W.A.: 65 Balcombe Way, Balga, 
Perth 6061. 49-4919. 

QLD.: L. E. BOUGHEN & CO., 
30 Grimes St., Auchenflower 
4066. 70-8097 

S.A.: ARTHUR H. HALL PTY. LTD., 
1-3 The Parade West, Kent 
Town 5067. 63-4506 

TELEX: Melb. 31447, Sydney 21707 


BULGIN BATT. HOLDERS 


A.R.6/72 


Name 


Address... 


Why Do Things 
The HARD Way? 




















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Simply 
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All States coverage 

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W.A.: Warburton Franki (Perth), 173 Hay St., East Perth 6000. 25-7787 

ALQ28/FP 


72 


ELECTRONICS Australia, June, 1972 






















the high tension secondary, in terms of 
voltage and current, varies with the size of 
transformer and the receiver which it is to 
supply. A small transformer, to supply a 
small mantel radio receiver, might 
typically have a HT secondary rating of 150 
volts either side of the centre tapping, at a 
nominal current rating of 30 milliamps — 
this figure referring to the permissible DC 
load current. 

A large transformer, intended to supply a 
television receiver, or amplifier, might 
have a voltage rajting per side of up to 400 
and a nominal DC load current of up to 250 
or even 300 milliamps. 

The two ends of the HT secondary winding 
are connected to the two plates of the rec¬ 
tifier valve, as depicted. This valve is 
virtually two diode elements in the one 
envelope, the plate and filament structure 
bejng expressly designed to carry a con¬ 
siderable amount of current. 

A valve of this type, intended for use in a 
power supply and having two separate 
anodes or plates, was commonly referred to 
as a full-wave rectifier. 

The filament of the rectifier is fed from a 
separate winding on the transformer, which 
is typically rated to deliver five volts at two 
or three amperes. It is quite usual for 
rectifier valves to consume considerable 
heater or filament power, the cathode or 
filament being designed to provide copious 
electron emission and thus allow the valve 
to pass heavy current without danger of 
early failure in service. 

To follow the action of the rectifier, 
consider the instant when a positive voltage 
has appeared on the left-hand half of the HT 
secondary and therefore on the upper 
rectifier plate, as drawn. 

Since the plate is positive, electrons will 
tend to flow to it from the heated filament. 
We can consider the result in a couple of 
ways, both of which lead to the same con¬ 
clusion : 

(1) In losing electrons, which are 
essentially negative charges, the filament 
of the rectifier must itself become positive. 

(2) When conduction takes place through 
the rectifier, the impedance of the filament - 
to-plate path in the valve must decrease. 
The filament must, therefore, approach the 
plate potential, and, since this is tem¬ 
porarily positive, the filament must tend 
also to become positive. 

Whichever way one cares to look at it, the 
result is the same — a positive potential on 
the plate and conduction through the valve 
produces a positive voltage at the filament. 

When the same plate swings negative, 
during the next half-cycle, there is no 
conduction through the valve and, 
therefore, no tendency for the filament to 
develop a simultaneous negative potential. 

On the contrary, aslhe first plate swings 
negative, the second plate simultaneously 
becomes positive and conduction takes 
place between the filament and this second 
plate. Once again, therefore, the filament 
tends to be carried positive. 

In other words, during successive half 
cycles, when each plate in- turn swings 
positive, current flow through on half of the 
rectifier or the other tends to carry the 
filament positive also. Since there are 100 
half cycles per second with 50Hz power 
mains, 100 positive pulses are apparent at 
the rectifier filament per second. 

The 50Hz alternating yoltage at the 
rectifier plates is thus changed to pulsating 


DC at the rectifier filament, positive with 
respect to chassis and having a heavy ripple 
content of 100Hz. 

This positive voltage is generated at the 
rectifier filament quite independently of the 
five-volts AC coming from the transformer 
winding to heat the filament. This latter 
voltage, applied across the rectifier 
filiament, raises it to operating tem¬ 
perature. When the positive voltage is 
generated, it carries the filament as well as 
the transformer winding feeding it, to a high 
positive potential in respect to chassis. 

Obviously enough, since the rectifier 
filament winding is expected to be at a 
positive potential with respect to chassis, it 
must not be earthed. 

Instead a wire connected to one wire of 
the filament or its supply winding becomes 
the source of the positive potential which 



Figure 2: Voltage waveforms associated 
with rectification and filtering in a simple 
power supply. Filtering is necessary to 
produce smooth DC from the pulsating 
rectifier output. The waveforms shown 
are: (a) the transformer secondary 
voltage, (b) the rectifier output, (c) the 
effect of the choke, (d) the effect of the 
capacitor, and (e) the output DC. 

must ultimately be fed to the plates and 
screens of the remaining valves in the 
equipment. 

However, the plates and screens must be 
fed with substantially pure DC, not a 
voltage which has a very high ripple con¬ 
tent. To get rid of the ripple, it is necessary 
to use what is known as a filter system, 
which as shown in figure 1 may involve a 
filter choke or inductor and a number of 
filter capacitors. 

The inductor consists normally of a large 
number of turns of wire wound within a 
laminated iron core, much like that used for 
small power or output transformers. It 
must be capable of carrying the amount of 
current involved in the particular supply 
and, with this current flowing, must have an 
inductance usually of several Henries. 

In some older-type radio receivers a filter 
choke, as such, was not used. Instead the 
current from the pwer supply was passed 
through a winding around the pole piece of 
the dynamic speaker. This gave the 
requisite inductive effect for filtering, and 
the magnetic field created by the current 
served at the same time to energise the 
speaker’s magnet system. The so-called 
“field” winding on the loud-speaker 
therefore served a double purpose. 

It may be remembered that in an earlier 


chapter we learned that an inductor tends to 
resist any change in the amount of current 
flowing through it. If the current increases 
above average, part of the energy involved 
is diverted into creating a stronger 
magnetic field around the winding. If the 
current decreases, the magnetic field is 
reduced and returns some of its energy to 
the winding as current flow. 

As a result of this action, current flowing 
through a filter choke loses a good deal of its 
ripple content and becomes more nearly 
pure DC. This is illustrated in figure 2, 
where (a) represents the transformer 
secondary AC voltage, (b) the basic 
rectifier output, and (c) the effect of the 
inductor. 

As indicated earlier, capacitance is also 
involved in a filter system, its effect being 
more or less complementary to that of in¬ 
ductance. A capacitor tends to oppose any 
change in the potential or voltage across it. 
If the voltage rises above an average value, 
some of the energy involved is diverted into 
the capacitor as an extra charge. If the 
voltage then subsequently falls, the charge 
is released, tending to maintain the original 
potential. 

When one or more capacitors is connected 
between the B-plus supply line and earth, as 
in figure 1, they naturally tend to oppose or 
absorb the change in potential due to ripple 
from the rectifier. They charge on “peaks” 
and release energy subsequently to fill the 
“troughs.” Diagrammatically, the effect is 
as illustrated in figure 2d. 

If properly designed, the combined effect 
of the choke and capacitors is to completely 
eliminate the ripple content for all practical 
purposes, and the output from the supply 
becomes virtually pure DC. (see figure 2e.) 

The rectifier circuit of figure 1 is known 
as a condenser-input or capacitor-input 
filter, because the rectifier feeds directly 
into a capacitor. In the less common 
arrangement, where the rectifier feeds 
directly into an inductor, the filter is 
described as a choke input filter. 

Filter capacitors normally need to have a 
large value of capacitance, certainly not 
less than eight microfarads each. To obtain 
this capacitance in small space and with 
adequate working voltage, not forgetting 
price either, they are invariably electrolytic 
types, as described in an earlier chapter. 

The main point to remember about 
electrolytics is that they must be connected 
the right way round, with their positive 
terminal connected to the positive side of 
the circuit. 

In recent years, much higher values of 
filter capacitance have become practical 
and, as a result, chokes having much lower 
inductances will suffice for the same degree 
of filtering. In point of fact, many small 
power supplies these days do not use a 
choke at all, relying only on large 
capacitors to give an adequate storage and 
filtering effect. 

Readers may recall from the earlier 
chapter on semiconductors that a 
semiconductor diode behaves almost 
identically with a valve or thermionic diode. 
In view of this, it should not be very sur¬ 
prising to learn that semiconductor diodes 
can be used in rectifier circuits in place of 
diode valves. 

In point of fact, they are somewhat better 
suited to this task than valves, as they 
require no heating power and also tend to 
conduct more easily during the part of the 


ELECTRONICS Australia, June, 1972 73 





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Twin Output (0 

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Use for fuel and water tank, foun¬ 
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thread. Motor 24-32V. DC perfect 
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74 ELECTRONICS Australia, June, 1972 













































cycle when they are called upon to do so. 
They also have a longer life, and are more 
reliable in service. At present, their only 
disadvantage is that they tend to be 
vulnerable to damage from transient over¬ 
voltage “spikes” which are at times present 
on AC mains. 

Two semiconductor diodes can be used in 
a full-wave rectifier circuit similar to that 
shown using a valve in figure 1, the only 
difference being that the diodes do not 
require a filament wiring on the trans¬ 
former. They are simply wired with their 
cathode connections tied together as the 
output connection leading to the filter 
circuit and the load circuit, and each anode 
connecting to one end of the transformer HT 
secondary winding. 

This type of rectifier circuit is not often 
used where semiconductor diodes are 
employed, however, because it requires the 
diodes to have a high peak inverse voltage 
rating. The peak inverse voltage is the 
reverse-bias voltage which appears across 
each diode when it is “off” and the other is 
conducting. 

With the full-wave rectifer circuit, the 
reverse-bias impressed upon the diodes 
when they are non-conducting is actually 
2.828 times the half-secondary RMS 
alternating voltage, and this can require the 
use of costly diodes having a very high peak 
inverse voltage rating. 

Because of this, it is often more desirable 
to employ what is called the full-wave 
voltage doubler rectifier circuit whenever 
moderate to high voltages and currents 
must be rectified by semiconductor diodes. 
Figure 3 shows a circuit of this type. 

A single untapped secondary HT winding 


cycles when the top of the transformer 
winding is negative and the bottom positive, 
the “series” (upper) diode is reverse- 
biased and non-conductive. The “shunt” 
(lower) diode is forward-biased, however, 
being connected to the winding via the lower 
filter capacitor. 

It therefore conducts, and in doing so it 
charges the lower capacitor to the peak 
value of the alternating voltage appearing 
across the winding. The capacitor voltage is 
as shown, with its earthed end negative with 
respect to the top end. 

During the other half-cycle of the AC 
wave, when the top of the transformer 
winding is positive with respect to the 

SILICON DIODE 


current demands are very slight, it is 
possible to use a single diode valve or a 
single semiconductor diode in what is called 
a half-wave rectifier circuit. Such a circuit 
using a semi conductor diode is illustrated 
in figure 4. 

A single untapped transformer secondary 
winding is used as with the doubler, but this 
time it needs to provide an RMS voltage 
approximately equal to the required DC 
output voltage. One end of the winding is 
earthed and the other connects to the first 
filter capacitor via the diode. 

The circuit is in effect half the full-wave 
circuit, and the diode only conducts on 
every alternate half-cycle when the top of 


RECTIFIER 


I -^FILTER 
CAPACITORS 


► HT 
►SECONDARY 

► WINDING 


B+ TO 


PLATES. ETC 


63V (HEATERS) 


Figure 4: When only very low current drain is involved, a half-wave rectifier system 
may be employed. A valve rectifier could be substituted for the semiconductor in this 
circuit. 


bottom, the “shunt” diode is reverse-biased 
and non-conductive, while the “series” 
diode conducts. This time the upper 
capacitor is charged to the peak value of the 
AC secondary voltage, as it completes the 
circuit back to the lower end of the winding. 
The voltage across it has a polarity as 
shown. 

As may be seen, the two capacitor 



Figure 3: Most power supplies using semiconductor rectifiers use the full-wave 
voltage-doubling circuit as shown here. It suits the rectifiers better, and is more 
compact and economical. 


is used on the power transformer, and the 
winding is arranged to produce an alter¬ 
nating voltage of only half (approx) the 
required DC output voltage. It should be 
noted, in passing, that this makes the power 
transformer somewhat simpler than in the 
full-wave circuit, and consequently 
somewhat less bulky and costly to produce. 

Two semiconductor diodes are used as 
before, but this time th&y are connected in a 
different fashion. The first filter capacitor 
also undergoes a change, becoming two 
separate units which fill a more complex 
role than did the single unit of figure 1. 

Neither end of the transformer HT 
secondary winding is earthed. Instead, one 
end goes to the junction of the two series- 
connected filter capacitors, while the other 
end goes to the two diodes. One diode has its 
cathode connecting to the winding and its 
anode earthed, while the other has its anode 
connecting to the winding and its cathode 
connecting to the top of the uppermost filter 
capacitor and the DC output circuit. 

The operation is as follows: For the half¬ 


voltages add together, and the total 
pulsating DC voltage available for filtering 
is twice the peak value of the transformer 
winding RMS voltage. Under load this 
voltage drops toward twice the RMS 
voltage. 

The most important thing to realise about 
the voltage doubler circuit is that for a 
given and required DC output voltage, each 
diode has to deal with only half the voltage it 
would meet in a conventional full-wave 
circuit. Thus the doubler circuit allows the 
use of relatively inexpensive semiconductor 
diodes having but a moderate peak inverse 
voltage rating. 

The voltage doubler circuit found almost 
universal acceptance in valve television 
receiver power supplies and in many other 
places where high current is required at a 
fairly high voltage. Silicon diodes are used 
almost universally in this circuit, as they 
are most easily arranged to have the 
required peak inverse voltage and forward 
conduction current ratings. 

In power supplies where the voltage and 


the HT secondary is positive. The half¬ 
cycles when the winding voltage is reversed 
are not used. 

The half-wave circuit is thus rather 
inefficient, as it only uses half the energy 
available from the transformer. It is as a 
result only suitable for low current rec¬ 
tification and, as the diode has to have a 
peak inverse voltage rating of ap¬ 
proximately 2.828 times the DC output 
(which is approx, equal to the RMS voltage 
of the HT secondary) it is really only 
practical for low voltages as well. 

The half-wave rectifier circuit delivers 
only one pulse of DC for each AC input 
cycle, so that its DC output ripple frequency 
is 50Hz. This makes filtering somewhat 
more difficult compared to the 100 Hz ripple 
produced by the full-wave and doubler 
circuits. 

So far in this chapter, we have thought 
mainly in terms of power supplies required 
for the operation of valve receivers and 
equipment from the mains. Let us now look 
at the type of power supply required to 
operate transistor equipment from the 
mains. 

As we saw in an earlier chapter, tran¬ 
sistors are relatively low-voltage devices 
compared with valves. They typically op¬ 
erate with supply voltages of from 3 to about 
80 volts, whereas valves normally use 
somewhat higher voltages. 

Where transistor circuits are required to 
deliver appreciable amounts of power — for 
example, in the case of transistorised audio 
amplifiers — they must accordingly be 
supplied with higher currents than valve 
circuits of equivalent performance. This is 
simply because to deliver power, they must 
be supplied with power, and power is ef¬ 
fectively the voltage multiplied by the 
current. 

Figure 5 shows a fairly typical type of 
transistor power supply. The power trans¬ 
former has only one secondary winding, an 
untapped low voltage winding. This is 
connected to a so-called bridge rectifier 
circuit, using four silicon diodes or a 
selenium “stack” (as used in battery 

ELECTRONICS Australia, June, 1972 75 
































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76 ELECTRONICS Australia, June, 1972 
















charger rectifiers), and thence to a very 
high value filter capacitor Cl and a further 
regulator and filter circuit using a tran¬ 
sistor. 

The bridge rectifier is full-wave, in that it 
operates on both half-cycles of the AC wave. 
It differs from the full-wave circuit of figure 
1 in that it does not require a tapped supply 
winding, and it differs from the doubler in 
that it does not supply a DC output voltage 
twice that of the RMS input voltage. 

In the bridge circuit, two diodes conduct 
during each half-cycle. When the top end of 
the transformer Winding is positive, diodes 
Dl and D3 conduct, and when the lower end 
of the winding is positive diodes D2 and D4 
conduct. 

The peak reverse voltage across the 


formed by resistor R and capacitor C2, 
while the emitter becomes the output 
electrode and connects to the load tran¬ 
sistors which must be supplied with power. 

The simple resistor-capacitor filter 
circuit used to supply the base bias for the 
transistor is sufficient to provide adequate 
smoothing, because the base current 
required is relatively small. However the 
fact that the transistor is fed with well- 
smoothed base current means that its 
collector-emitter current — which is an 
amplified version of the base current — also 
tends to be well smoothed. Hence the 
relatively high current fed to the load 
transistors is smoothed, and the effective 
output voltage produced at the emitter of 
the filter transistor is also smoothed. 



Figure 5: Fully transistorised equipment normally needs a much lower supply voltage 
than valves but at a much higher current. This typical transistor supply shows a bridge 
rectifier system, a high value filter capacitor, and a transistor dynamic filter circuit. 


value given by the product of C2 and the 
transistor current gain. Thus, it is said to 
act as a “filter capacitance multiplier.” 

For example, if C2 has a value of 500uF 
and the transistor has a gain of 100, the 
effective filtering is considered to be 
equivalent to a capacitor of 50,000uF 
shunted directly across the load. 

While this comparison is fairly accurate 
as far as the filtering is concerned, it is not 
accurate as far as the source impedance 
seen by the load is concerned. This point is a 
little too involved for our purposes at 
present, but it should be remembered that 
the concept of “capacitance multiplication” 
is rather limited in its application. 

As mentioned earlier, a transistor con¬ 
nected like that in figure 5 (as an emitter 
follower, in other words) can also be used to 
“regulate” the output of a power supply. 
This means that it can be arranged to keep 
the supply voltage substantially constant at 
the correct value, despite changes in the 
current drawn. 

As you might have already guessed, this 
is done by holding the voltage supplied to 
the base of the transistor constant, so that 
the transistor has no choice but to maintain 
substantially the same voltage at its 
emitter. Usually the base voltage of the 
transistor is held constant by using a circuit 
with a so-called “Zener diode”, which is a 
special sort of semiconductor diode made to 
be operated in the reverse breakdown 
condition. The operation of the circuit 
depends upon the fact that the voltage drop 
of such a zener diode remains effectively 
constant for a wide range in currents. 


NPN POWER 
TRANSISTOR 



Figure 6: This transistor supply is similar to that of figure 5, but the transistor circuit 
performs voltage regulation as well as dynamic filtering. 


diodes when they are non-conductive is 1.414 
times the RMS supply voltage and (ap¬ 
prox) the DC output voltage, so that the 
bridge circuit is midway between the full- 
wave and doubler circuits in its demands 
upon the diodes regarding their peak in¬ 
verse voltage rating. 

The low-voltage, high current 
requirement of transistor power supplies 
makes filtering the AC ripple from the DC 
output a difficult task. A very large first 
filter capacitor is required (some supplies 
use 10,000 uF or higher), and as we have 
shown a transistor filter circuit must often 
be used for additional filtering. To maintain 
the output voltage constant under load it 
may also be necessary to add further cir¬ 
cuitry for regulating the output. 

The transistor is used to give what we 
might think of as “amplified” smoothing of 
the power supply output. Its operation relies 
upon the fact that the bipolar transistor is a 
current amplifier. It is capable of con¬ 
trolling large currents when supplied with 
small input or “bias” currents, as we saw in 
chapter seven. 

The general principle of transistor 
filtering and regulation is that the transistor 
is made to control the relatively large 
current drawn by the load circuit by sup¬ 
plying its control electrode — the base — 
with a smoothed and / or regulated source 
of bias current. As this reference source is 
required to supply only the-small control 
current of the transistor, it is a relatively 
easy matter to provide it with filtering and 
regulation. 

As may be seen from figure 5, the tran¬ 
sistor (here an NPN type) has its collector 
connected to the pulsating DC output of the 
rectifier. Its base is supplied with smoothed 
bias current by means of the filter circuit 


This type of transistor filter circuit is 
often called a “dynamic” filter, because the 
filtering is achieved by the transistor ef¬ 
fectively varying its instantaneous 
resistance to compensate for the pulsations 
at the rectifier output. Because the load 
voltage tends to duplicate the reference 
voltage at the base of the transistor, a 
transistor connected in this way is also said 
to be connected as an “emitter follower”. 

The feature of the emitter follower mode 
of connection which is of particular im¬ 
portance from the viewpoint of dynamic 
filtering and regulation, is that the load 
voltage is more or less independent of the 
transistor collector voltage. As long as 
there is sufficient collector supply voltage 
to supply the requirements of the transistor 
and load, any pulsations or variations 
present in the collector supply voltage tend 
to have little if any effect upon the load 
current and voltage. 

Often the action of a dynamic filter is 
pictured by considering the transistor to 
have “amplified'’ the filter capacitor C2 to a 


Figure 6 shows the circuit of a very 
simple regulated power supply using a 
zener diode. Basically the supply is iden¬ 
tical to that of figure 5, but the resistor in 
the base circuit is now divided into two, with 
capacitor C2 now connected between their 
junction and the negative line (which is 
earthed). The zener diode is connected 
between the transistor base and negative, 
holding the base above ground by the diode 
breakdown voltage. 

In closing the discussion of power sup¬ 
plies, filtering and voltage regulation, it 
should be mentioned that, although the 
principles of dynamic filtering and 
regulation have been explained by 
reference to transistors, the same prin¬ 
ciples apply to valves. Dynamic filtering is 
not often employed in valve circuits — 
principally because it is fairly easy to 
achieve adequate filtering using normal 
inductor-capacitor filters — but valve-type 
voltage regulators are quite often used in 
test equipment and other equipment 
requiring well-regulated supply voltages. 


ELECTRONICS Australia, June, 1972 77 








































THE BRILLIANT NEW 


THE BRILLIANT NEW 
WHARFEDALE RANGE 

From the very birth of the term “high 
fidelity”, British manufacturers have set 
world standards for the design and 
fabrication of the most outstanding high 
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Famous Wharfedale loudspeakers have 
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a complete range of fully compatible 
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Let’s look at the new era Wharfedale 
range:— 

THE NEW ERA WHARFEDALE “LINTON” 
STEREO AMPLIFIER 

The new era Wharfedale “Linton” stereo 
amplifier is attractively styled, power output 
is 15 watts R.M.S. per channel into 8 ohm 
speaker loads, and frequency is 30-20,000 
Hz. ± 1 dB. at full rated output. 

Sensitivity of the new era “Linton” 
amplifier suits magnetic stereo cartridges at 
3.5 mV. and T.H.D. does not exceed 0.1% 
at 1 kHz. into 8 ohm speaker systems at 
full output. 

Tone controls for bass and treble response 
offer unusual flexibility . . . piano-key 
switches are provided for mode, treble 
filter, tape monitor, tape input, phono input 
and tuner. Ask for a no-obligation 
demonstration at any Simon Gray dealer! 


THE NEW ERA WHARFEDALE “LINTON" 
TURNTABLE 

Designed to take records of 7", 10" and 
12" diameter, the new era “Linton” turn¬ 
table also features four speeds — 16%, 

33V 3 , 45 and 78 r.p.m. 

You may adjust the “Linton” turntable for 
either Manual or Automatic operation, 
switch-off and return are automatic, stylus 
tracking pressure is fully adjustable, a bias 
compensator is incorporated and the arm 
lowering device is hydraulically damped to 
protect your records. 

The magnetic stereo cartridge fitted is the 
well known Shure M44-7, complete with 
diamond stylus. 

THE NEW ERA WHARFEDALE “LINTON 2” 
COMPACT SPEAKER SYSTEM 

Featuring an entirely new 8" speaker with 
an oversize magnet which produces 
exceptional performance, the new era 
“Linton 2” is both attractive and compact. 
Frequency response is 55-17,000 Hz. ± 

3 dB. and power handling capacity is 20 
watts DIN. Size is only 19" x 10" x 9V2" 
and finishes available include oiled teak and 
polished walnut. A new 2" tweeter unit 
covers all frequencies from 1,200 Hz. 

THE NEW ERA WHARFEDALE “LINTON 3” 
COMPACT 3-WAY SPEAKER SYSTEM 

Identical in cabinet design and size to the 
2-way "Linton 2”, the addition of a 4" mid¬ 


range speaker to the speaker complement 
brings smoother overall frequency response 
and added “presence” to stereophonic 
playback. 

Frequency response is 55-17,000 Hz. ± 

3 dB., and power handling capacity is 25 
wats DIN. Size is 19" x 10" x 9V2". 

THE NEW ERA WHARFEDALE MODEL DC9 
CASSETTE TAPE RECORDER 
With the Dolby System ! 

The release of the new era precision built 
Wharfedale Model DC9 Cassette Tape 
Recorder heralds a major breakthrough for 
cassette recording. 

Precision tape transport mechanism is used 
in the new era Wharfedale DC9. 

Frequency response 50-12,000 Hz. ± 2 dB., 
wow and flutter less than 0.18%, signal-to- 
noise ratio better than 50 dB. 










WHARFEDALE RANGE! 


two-way speaker system in its own right. 
Impedance is 8-16 ohms and frequency 
response is 16-22,000 Hz. Distortion is less 
than 1%, an extraordinary figure for a 
stereo headset. 

THE COMPACT NEW ERA WHARFEDALE 
“DENTON 2“ AND “DENTON 3“! 

Although they measure only 14" x 9%" x 
8%", both models of the “Denton” sound 
like much larger systems. 

The “Denton 2” uses an 8" long throw 
voice coil bass reproducer and a 2" tweeter, 
with an electrical crossover at 1,400 Hz. 

Bass and mid-range performance is quite 
remarkable for an enclosure of these 
physical dimensions. Frequency response is 
60-16,000 Hz. ± 3 dB. and power rating is 
20 watts DIN. 

In the “Denton 3” a 4" mid range speaker 
is added. Frequency response is 
65-17,000 Hz ± 3 dB. and power handling 
capacity is 25 watts DIN. Crossover 
frequencies are 1,100 Hz. and 4,000 Hz. 
respectively. 


TWO NEW MEDIUM SIZE, MEDIUM PRICE, 
HIGH PERFORMANCE SPEAKER SYSTEMS 
FROM WHARFEDALE . . . NEW ERA 
“MELTON 2” AND THE “DOVEDALE 3”! 

The Wharfedale “Melton 2” is a 2-way 
speaker system which sounds as if is costs 
much more. Measuring only 
21" x 14V2" x 10" it incorporates a 
12" wide spectrum bass reproducer and a 
specially designed 2" C.A.B. tweeter; 
power handling capacity is 25 watts DIN. 
Frequency response is 45-17,000 Hz 
± 3 dB. Impedance is nominally 6 ohms 
and finishes available are oiled teak and 
polished walnut. 

With the release of the “DOVEDALE 3” 
Wharfedale have produced the 
smoothest overall frequency response 
ever available in a Wharfedale enclosure. 
With a 12" bass reproducer, a 5" mid-range 
speaker and a 1" tweeter, frequency 
response of the “Dovedale 3” is 45-20,000 
Hz ± 3 dB. and power handling capacity 
is 50 watts DIN. Crossover frequencies 
are 600 Hz. and 5,000 Hz. “Dovedale 3” is 
24" x 14" x 12" 


THE NEW ERA WHARFEDALE “TRITON 3”! 
In the new era "Triton 3” an 8" bass unit 
is complemented by a 5" mid-range 
speaker and an effective 1" tweeter. The 
combination offers restraint-free bass 
response, smooth middle frequencies with 
remarkable “presence” and outstanding 
high frequency performance. 

Here are abridged specifications: Size: 

21 %" x 9%" x 9". Frequency response: 
55-20,000 Hz ± 3 dB. Speakers: 8" bass, 

5" mid-range and 1" tweeter. Crossover: 

750 and 5,000 Hz. Impedance: Nominally 
6 ohms. Power rating: 25 watts DIN. 
Finishes: Oiled teak or polished walnut. 

THE NEW ERA WHARFEDALE “ROSEDALE” 

Built to the highest standards without 
compromise, the new era Wharfedale 
“Rosedale” offers a wide frequency 
response of 35-20,000 Hz. without 
coloration and a power handling capacity 
of 45 watts DIN. 

Few speaker systems can handle this 
power, and only a handful do it well. 

The new era Wharfedale “Rosedale” leads 
this select band. 



House, Smith Street, Da 
ti, Brisbane. 58 1422. 
V.A.: Athol M. Hill Pty. I 









3-Channel Mixer 

It is a number of years since we published a microphone mixer — more 
than five to be fexact. So we thought it about time to publish another. This 
mixer, however, is quite different from any we have published in the past — 
it should not cost more than six dollars to build. 


Elementary 

Electronics 



by ROSS TESTER 


There are many situations where it would 
be very convenient to be able to mix the 
outputs from a number of signal sources. 
This little mixer, with three input channels, 
will do a first class job, in spite of its sim¬ 
plicity. 

We would envisage that it would be quite 
acceptable for use at school concerts, 
speech days, etc. Therefore, it would make 
an interesting and economical project for 
members of Youth Radio Clubs, etc. 

Each channel has an input impedance of 
280K and is suitable for use with any 
medium to high impedance dynamic mi¬ 
crophone. It will give approximately 30mV 
out for 5mV in, thus making it suitable for 
feeding into the preamplifier of a PA am¬ 
plifier, tape recorder, etc. 

The input impedance is too low for crystal 
microphones, but it should be possible to 
modify the circuit to suit. For any input 
intended for 3 crystal microphone the 
potentiometer and associated resistor 
should be increased to 4.7M. The unit can 
use a mixture of crystal and dynamic input 
channels if desired. 

However, be aware that such high im¬ 
pedance circuits are much more prone to 
hum pick up. Where they are used it may be 
necessary to shield the mixer completely, 
inside a metal box. For these, and other, 
reasons the dynamic microphone is 
generally to be preferred to the crystal 
type. 

Another possibility is to use one of the 
channels for a crystal pickup, rather than a 
microphone. A crystal pick will have a 
much higher output than a dynamic 
microphone, and also requires a much 
higher load impedance to deliver a proper 
bass response. The easiest way to cope with 
these two requirements is to connect a 




The front panel 
our mixer. The 
layout is not critical 
and other panel 
arrangements could 
be used. 


resistor of about 2.2M in series with the 
active lead from the pickup. This resistor 
may need to be shielded to prevent hum 
pick up. 

How does this mixer circuit work? It is 
what is called a passive system, since it 
does not depend on active devices such as 
valves or transistors for the mixing func¬ 
tions, as such. It consists simply of three 
pots, as volume controls, and three resistors 
of the same value. 

In its crudest form a mixer might consist 


and this is one reason we follow it with an 
amplifying stage. 

The amount of loss depends on the 
number of input circuits we provide. In the 
simplest case, where we mix only two in¬ 
puts, the loss will be two to one in the worst 
situation. That is to say, with one input 
turned full on, and the other right off, only 
half the signal fed to the input will appear at 
the output of the mixer. With the three 
stages shown, and two turned off, the loss is 
three to one. 



The circuit of the mixer. The mixing circuit proper consists of the three 470k pots and their 
associated 470k isolating resistors. The amplifier stage helps make good the losses in the 
mixer network. 


of just three pots, with their moving arms 
connected together and fed to the amplifier 
input. Such an arrangement would work — 
in a fashion — but would suffer from very 
serious interaction. For example, if the 
moving arm of any one pot was turned to the 
full off position, it would kill the output of 
the other two. 

This is the reason for the isolating 
resistors in series with the arm of each pot. 
Even when a pot is turned fully off, there is 
enough resistance between it and the rest of 
the circuit to minimise its effect. Note that 
we say minimise, because it will have some 
effect. However, it will be slight, and of 
little practical importance. 

As might be expected, a simple circuit 
like this must impose some penalty. The 
penalty is an overall loss in the network, 


Output from the mixer network goes to 
the amplifier stage, a 2N5485 FET in this 
case. The high input impedance of the FET 
is well suited to this application, since it 
minimises any loading on the mixer net¬ 
work. 

The voltage gain of the mixer is deter¬ 
mined by the gain of the FET, less the losses 
in the mixer circuit. The gain of individual 
FETs varies widely, but we would expect it 
to be somewhere around 20. In our case, a 
5mV signal fed to one channel, with the 
other two off, gave an output of 27mV, or an 
overall gain of a little over 5. Allowing for a 
3 to 1 loss in the mixer, this gives a gain in 
the amplifying stage of about 16. 

The output impedance is approximately 
equal to that of the drain resistor, or 10K. 
This means that a main amplifier with an 


ELECTRONICS Australia, June, 1972 


80 


































input impedance of around 50K would not 
seriously load the mixer. As the impedance 
is reduced below this point there will be 
some increase in distortion but, considering 
the limited signal level in this part of the 
circuit, it should be safe to work into a 20K 
load without a serious increase in distortion. 
It would be unwise to go below this value. 

Note that the supply line to the FET drain 
is decoupled with a 50uF electrolytic 
capacitor and a 2.2K resistor. The main 
purpose of this is to minimise a rather 
disturbing “crack 1 ’ which can occur in the 
speakers if the mixer should be switched on 
or off while the main amplifier is running. 
Even with this network there may still be a 
“thump 11 , and it is a good idea to turn the 
main amplifier gain down before switching 
the mixer on or off. 

Perhaps the best place to start in the 
construction of the mixer is the metalwork. 
A simple “L” shape bracket, as shown in 
the illustrations on the right, should present 
no problems, even for the novice. 

We made our mixer on a piece of scrap 
aluminium measuring 7*i>in (190mm) wide 
by 5*4 (133mm) deep, bent at right angles 
2in (51mm) from the top. This gave us a 
compact unit, which could be used as it was, 
or built into a case. However, these 
dimensions are not critical, and, providing 
adequate care is taken with shielding, no 
problems should result from any change in 
layout. In fact, a change may be preferred, 
as some operators find it annoying to have 
the jacks emerging close to the control pots. 

Once the holes are drilled, the aluminium 
can be bent as indicated. Hold it in a 
vyce, between two pieces of metal with a 

PARTS LIST- 

Resistors: (1/2 watt) 

1 x Ik 

1 x 2.2k 

1 x 10k 

1 x 470k 

2 x 470k log pots 

1 x 470k log pot with switch 

Capacitors: 

3 x .022uF LV ceramic or polyester 

1 x 0.33uF LV ceramic or polyester 

2 x 50uF 25VW 
1 x 2N5485 FET 

3 x input sockets (see text) 

1 x output socket (see text) 

2 x 9V batteries with connectors (Eveready 

216 or sim) 

3 x knobs to suit 

3x 'Ain, Va Whitworth csk head screws and 
nuts. 

1 x 10 lug tags trip (E-8-E) 

2 x battery damps (see text) 

1 piece 18-20SWG aluminium , size to suit. 
1 length shielded cable , approx 8in. 
(200mm) 

1 length tinned copper wire (or hookup 
wire), approx 6in. (150mm) 

1 sheet Letraset (for front panel labels if 
required). 

Note: Resistor wattage ratings and 
capacitor voltage ratings are those used 
for our prototype. Components with 
higher ratings may generally be used 
providing they are physically com¬ 
patible. Components with lower ratings 
may also be used in some cases , 
providing the ratings are not exceeded. 




good straight edge. Line the aluminium up 
with the straight edge, and tighten the vyce. 
Then, with a block of wood, bend the 
aluminium until it is as close as possible to a 
right angle. Then take a hammer and a 
block of wood, and strike the block while 
moving it back and forward along the bend 
until it is square. 

Next, the pots and jacks should be fitted, 
and the input components soldered between 
them. Wire the tag strip before mounting it, 
soldering the FET in place last to minimise 
risk of damage to it due to excessive heat. 

It should be possible to wire the mixer 
completely using only the circuit diagram, 
but for those with limited experience we 
have provided a photograph and a detailed 
wiring diagram. Using all these sources of 
information, even the beginner should have 
no trouble. 

We used countersunk-head screws to fix 
both the tagstrip and battery clamps. The 
head should be flush with the underside of 
the base, so as not to scratch any surface 
they might be put on. Four rubber feet in the 
corners would also preclude this from 
happening. 

Shielded wire should be used for all the 
signal circuits. This is necessary to 
minimise hum pick up from stray AC fields, 
and also RF energy from any nearby radio 
or TV transmitters. If hum or RF pickup 
should still be a problem, it may be 
necessary to enclose the wiring completely, 
in a metal box. 

For those not used to handling shielded 
cable, a few points may help. When 
soldering to either the inner conductor, or 
the outer braid, take care not to damage the 
insulation between them, which has a low 


POTENT! 

ITERS 


-TT-V _ 


****** 




u— 


-m* 

WIREWOUND 

single to multi-turn 
sealed and unsealed 

TRIM POTS 


helical— analog digital 1 dials to suit 
I See the Specialists in Components and Service 




Hawker Siddeley 
Electronics 


SYDNEY 93 0221, MELBOURNE 387 1899, 
BRISBANE 47 4311, ADELAIDE 46 5941, 
PERTH 71 8766. 


ELECTRONICS Australia, June, 1972 


81 


(70/1X71 







































































LAFAYETTE GUARDIAN "6000” 6-BAND 


Beacon - Broadcast - Marine - FM - Aircraft - VHF 
Portable Radio with Radio Direction Finder 



Rotatable Antenna 
for Beacon, Broadcast & 
Marine Band Reception 
& Direction Finding 


$179.50 

Including 
Sales Tax 


Signal Strength 
Tuning/ Battery 
Meter 


/ 


Tunes 
6 Bands 


Squelch 

Control 


BATTERY OR 240V AC OPERATION 

6 BANDS (1) 180-380 KHz (2) 540-1600 KHz Broadcast (3) 1.6-4.6 
MHz Marine (4) 88-108 MHz FM (5) 108-136 MHz Aircraft (6) 147- 
174 MHz FM VHF 

The Guardian "6000” is Lafayette’s most advanced deluxe Portable Battery/Electric 
Radio for top reception plus Direction Finding, 19 Transistors, 14 Diodes and 2 Therm 
istors. Complete with comprehensive Operating Manual. 


HA-600A Solid State Communications Receiver 



GENERAL 

COVERAGE 

HA-600A 

$219.50 

Including 
Sales Tax 


g BANDS 150 400 KHz ' 55 °- 1600 KHz (Broadcast Band), 1-6-4.8 MHz, 4-8-14.6 MHz, 

OPERATES FROM 12 VOLTS DC (negative ground) OR 220-240 VOLTS 50 Hz 

• Field Effect Transistors in R.F., Mixer and • Edge illuminated Slide Rule Dial with "S'* 
Oscillator Stages. Meter. 


• Two Mechanical Filters for Exceptional 
Selectivity. 

• Voltage Regulated with Zener Diodes. 

• Product Detector for SSB/ CW. 


• Continuous Electrical Bandspread Calibrated 
80—10M. Amateur Bands. 

• Variable BFO, Automatic Noise Limiter. 

• Speaker Impedance: 4 to 16 Ohms. 


LAFAYETTE ELECTRONICS 

Division of Electron Tube Distributors Pty. L AFAY£TTC Communications Receivers an also 

available from :— 


All mail enquiries and orders to: 

VICTORIAN SALES CENTRE 
AND HEAD OFFICE, 

94 HIGH STREET, ST. KILDA, 
VIC., 3182. Phone 94 6036 


RADIO HOUSE PTY. LTD., 306 Pitt Street and 760 George 
Street, Sydney, N.S.W. 

TISCO AGENCIES, Overend and Hampton Streets, 
Woolloongabba, Q’land. 

WILLIS TRADING CO., 445 Murray Street, Perth, W.A. 

L A. HEYWARD, 6 Herbert St, Launceston, Tas. 


TRADE REPRESENTATIVES 


S.A.: Tyquin Distributors Pty. Ltd-, 13 Deacon Ave., Richmond — Phone 57 8153. 
W.A.: Athol M. H±\\ Pty. Ltd., 613-615 Wellington St., Perth — Phone 21 7861. 


melting point. Experiment on a few scrap 
lengths first. 

If the outer shield is simply wrapped 
around the insulation, it is quite easy to 
separate the two. If it is braided, we suggest 
that you push the strands of the braid apart 
until there is a hole large enough to allow 
the inner conductor to be pulled through it. 
Again, experiment with a scrap. 

We have not shown any diagram for the 
battery clamps. These are made by bending 
a piece of thin metal around the batteries 
themsleves, and then drilling the mounting 
holes. You may use thin aluminium, as we 
did, or tinplate, etc. They are both secured 
to the chassis by the same screw, and the 
batteries are clamped underneath. 

The batteries in are connected in series, 
with the on-off switch between them. 
Putting the switch in this position is con¬ 
venient because the switch now also serves 
as an anchor point for the connection be¬ 
tween the two batteries. 

Some readers may think we have 
forgotten part of the wiring around the input 
sockets, as these appear to have only one 
connection made to them, rather than the 
two shown in the circuit. The explanation is 
simple; mounting the sockets on the metal 
panel makes contact to one side of them, 
and we use the metal panel as a common 
conductor. 

Note that, while we can employ this 
technique in a simple battery operated 
device like this, there are many situations 
where it would not be satisfactory. Par¬ 
ticularly where AC from a power supply 
may flow through the metal chassis, there is 
a high risk of hum pick up. In such cases all 
such terminals should be insulated from the 
chassis and wired to a common point. 

After finishing the wiring unscrew the 
tagstrip and battery holders, remove the 
nuts from the potentiometers and sockets, 
and lift the whole of the circuitry out. Then 
you will be able to polish the front of the 
panel with some fine emery cloth, which 
removes the marks and scratches from it. 
Then, to provide a neat finish, “scratch 
grain’’ the panel with a wire brush. This is 
done by holding the aluminium over the 
corner of a bench, and scratching the 
surface with a wire brush, in one direction 
only. 

Taking care not to touch the front again, 
make up the lettering using “Letraset” or 
similar rub-on lettering. The “Letraset 
Printpack’’ is an economically priced pack 
well suited to small jobs of this kind. Even 
the dots which mark the pot positions are 
made this way. The Letraset Printpak No 8 
would be the best to buy. It contains type 3 
and 4mm high, which would be suitable for 
most panel marking. 

Finally, give the whole panel a fine coat of 
clear flat enamel from a spray pack. This 
protects the surface from fingermarks and 
also stops the letters from lifting. 

Then re-assemble the circuitry on the 
panel. It may seem a little odd to remove it 
all after the job is completed, but if the 
lettering is done in the preliminary stages 
it will almost certainly be damaged in some 
way. In any case, the way we assembled the 
circuitry makes it easy to remove in one 
lump. 

And that’s about all there is to it. Follow 
our instructions carefully and you should 
have a versatile little unit which will in¬ 
crease the usefulness of any amplifier by a 
very large factor. 


82 


ELECTRONICS Australia, June, 1972 






























Elementary Electronics-. 
-yA J Ideas Worth Trying 


Low Cost Reversing Light For Cars 


I was confronted with the need to fit 
backing lights to my car. As the car was 
new, I did not wish to mar the appearance 
by fitting additional lights, so I fitted the 
following additions to the flasher circuit, to 
make the flasher lights double as reversing 
lights. 

I bought a reversing switch and fitted it to 
the place provided on the gearbox. Most 
cars — even fairly old ones — have 
provision for the switch on the gearbox. The 
reason for this is that in the past, only the 
luxury versions had reversing lights, but 
the gearbox housing used was the same as 
in the standard models. This is especially 
true of Continental cars. 

As can be seen from the circuit diagram, 


the rear orange turning indicator lamps can 
be used as reversing, lights merely by 
bypassing the flasher mechanism, and 
isolating the front and rear circuits by 
means of silicon diodes. This method does 
not alter the outward appearance of the 
vehicle, but the increased night safety plus 
the low cost — the price of four diodes plus 
the switch — should make this idea popular 
with owners of both old and new model cars. 

Some readers may have cars with no 
provision for a gearbox switch. If this is the 
case, a switch could be mounted on the 
dashboard to perform the same function. If 
this is used, there should be some sort of 
warning lamp to indicate that the reversing 


lights are on. This may be a legal 
requirement in some states. 

The diodes should have a PIV at least 
equal to the maximum voltage likely to be 
generated in the car’s electrical system, 
and a current rating equal to the surge 
(cold) current of the lamps. The largest 
flasher lamps appear to be 18W types; 1.5A 
at 12V or 3A at 6V. Assuming a cold 
resistance of about one eighth of the hot 
resistance — which appears to be typical — 
the surge current in a 6V system could be 
about 25A. 

On the basis of these figures, the most 
logical choice is the type of diode used in 
vehicle alternator systems. These are 


usually rated at 25A continuous, with a 
surge rating well in excess of this, and a 
PIV of around 200. A typical type is the 
BYX21L / 200. This type of diode also re¬ 
presents about the best value for money 
available, considering the ratings and the 
safety margin which they represent. 

Also, with ratings of this order it may be 
permissible to omit the two diodes isolating 
the front flasher lights, particularly in 12V 
systems. This would mean that the front 
lights would be energised as well as the rear 
ones, but there does not seem to be any 
serious objection to this. 

(Idea submitted by: Mr L. Junor, 
Bronaldi St, Heathmont, Victoria 3135.) 


There's a place 
foryou In the 
growing world 
of electronics 

Whether you’re a hobby 
enthusiast or have professional 
ambitions, a Stott’s course will 
help you find it. 

Every day the number of applications 
for electronics in industry, science and 
business increases. It’s a field which 
offers valuable career opportunities in 
manufacture, installation, servicing 
and sales-but only for people with 
thorough training. 

That’s why Stott’s have just introduced 
an important new course, Introduction 
to Electronics. It combines both the 
theoretical and practical aspects, and 
includes a number of experiments to 
give you experience in the construction 
of electronic equipment. Extensive kits 
are supplied with the course. 

Other Stott correspondence courses 
will help you become expert in the 
theory and practice of radio communi¬ 
cations, or give you the know-how to 
get an Amateur Operator’s certificate: 
Radio for Amateurs Course: 

From radio basics, to intricate prin¬ 
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tion. Latest techniques in electronics. 
Everything you’ll ever need to know, 
made easy to understand by top radio 
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Gives you the background knowledge 
and the skills you need to pass the 
PMG exams and get your Certificate of 
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Make your place in the world of 
electronics. Start today by sending in 
the coupon below. 



■ Stotts W 

| TECHNICAL CORRESPONDENCE COLLEGE 

I 159 Flinders Lane, Melbourne, 3000. 383 
™ George St., Sydney, 2000. 290 Adelaide St., 
Brisbane, 4000. 45 Gilles St., Adelaide, 5000. 
89 St. George’s Terrace, Perth, 6000. P.O. 
Box 3396, Singapore 1. 

Please send me, free and without obligation, 
full details of your courses in Radio and 
Electronics. 


| Mr., Mrs., Miss 



1C OFFER — SPECIAL ANNOUNCEMENT 

Reader response to the special offer of a low price linear 1C in our April issue was 
quite overwhelming. Fairchild Australia Pty Ltd had a stock of many thousands of 
the FuA703 devices, but within two weeks of publication of the April issue we were 
advised that Australian stocks had been virtually exhausted. Additional supplies 
were ordered immediately from overseas, but there has been an unavoidable 
delay in servicing some reader requests. Fairchild Australia and Electronics 
Australia apologise for any inconvenience created by this delay. 

NOTE: Because of the enormous response to date and the limited overseas 
supplies of these devices, the offer must be closed to Australian readers on Friday 
June 9th. Coupons and remittances which reach Fairchild Australia later than this 
date cannot be serviced, and will be returned with apologies. However New 
Zealand readers are assured that stocks are being reserved for them. 



The addition of four diodes, a reversing light switch, and a fuse, added to a conventional 
flasher circuit, enables the flasher lights to double as reversing lights. 


ELECTRONICS Australia, June, 1972 


83 






























The amazing case of 
the house with the moving walls. 



This is a house in Frenchs Forest. With moving walls. 

It’s true. 

They move outwards. 

Before your very ears. 

The explanation has nothing whatever to do with the 
supernatural. 

Or at least not as we normally understand it. 

The reason — the owner has a pair of Sonab speakers. 
Sonab speakers are omnidirectional. 

They fill an entire room with rich true stereo sound. 
Instead of that one short static line you get from 
conventional forward facing systems. 

But they also have another unique feature. 

Listen to Sonab speakers, close your eyes, and you’ll find 
that the effect is of moving the walls behind the speakers 
outward. Away from you. The whole room seems to open 
up. It’s a difficult phenomenon to describe. But it’s one 
that every Sonab owner has experienced. 


If you're cynical there’s only one way to prove it to you. 
We’d like to come demonstrate the effect in your own 
home. 

Just invite us. 



Sonab 

Sonab of Sweden Pty. Ltd., 114 Walker Street, North Sydney, N.S.W. 2060. Telephone: 929 4288/4554. 

84 ELECTRONICS Australia, June, 1972 




























CLASSICAL 

RECORDINGS 

Reviewed by Julian Russell 


Holst's Planets Suite — "exciting performance' 


HOLST — The Planets (suite). Los Angeles 
Philharmonic Orchestra with the female 
voices of the Los Angeles Master Chorale 
conducted by Zubin Mehta. Decca Stereo 
SXL6529. 

For the benefit of those to whom this 
splendid work is unfamiliar — and there 
cannot be many among the readers of this 
column — Holst used the planets in their 
astrological sense. Thus the first, Mars, is 
sub-titled The Bringer of War. Mehta starts 
it quietly, using a steady, sinister rhythmic 
tempo restrained in dynamics until the first 
climax, which is altogether shattering. The 
dirge-like middle section is in effective 
contrast and the playing and recording are 
quite wonderful. 

In Venus, the Bringer of Peace, I thought 
the four-note rising phrase on the horn 
lacked variety in its many repetitions, and 
later, the violin solo a bit sentimentalised. 
Mehta’s reading is highly individual. It 
suggests to me to try to express the deep joy 
of peace and not, as is more usual, its easy, 
cool security. 

Mercury, the Winged Messenger, has 
quicksilver slipperiness instead of the 
customary fleetness though it too is 
beautifully played right up to tempo. Later, 
at the entrance of the solo violin, it seems to 
get altogether too rarefied and generally 
speaking something more definite in the 
way of contrasts would have been welcome. 

I think most will agree that Jupiter, the 
Bringer of Jollity, is a complete success. 
Mehta’s reading has true Jovian jocularity, 
full of rumbustious belly-laughter. In the 
middle section the great open-air hymn-like 
tune is given truly majestic stature. Playing 
and recording alike are peerless. In the 
opening bars of Saturn, the Bringer of old 
Age, you have hopeless, comfortless wind 
chords against superbly recorded double 
basses. The weariness of the slow march¬ 
like theme in the middle section also comes 
off splendidly. Mehta tries to shake off this 
weariness in a restrained climax raised to 
just the right level. And the piece ends with 
the threatened change of senility into 
dissolution. 

Uranus, the Magician, offers just the 
right mixture of musical sleight of hand and 
swaggering braggadocio. By the way 
have Queensland readers ever noticed how 
much the opening four notes resemble the 
call of their butcher bird? The inspiring 
dotted note march, which starts off way 
down in the lowest brass and goes all the 
way up to high piccolos, -leads to an 
altogether magical effect of a sudden 
change from ultra fortissimo to barely 
heard pianissimo which nearly had me 
jumping out of my seat. 

I must confess to having been disap¬ 
pointed in Neptune, the Mystic. Holst in this 
takes you right out into the unbearable cold 


of interstellar space. But I thought Mehta’s 
interpretation altogether too prosaic, 
without even a hint of mystery or blackness. 
And even when the well-drilled choir enters 
with its quiet, wordless chorus, there is no 
improvement. But, for the rest, if you’re 
willing to suspend preconceived ideas about 
how the different components of this suite 
should go, this is an exciting performance, 
give or take an occasional bar. 

★ ★ ★ 

DEBUSSY — String Quartet in G Minor. 
BLOCH — String Quartet No. 3. The Carl 
Pini Quartet. EMI Stereo SOXLP 7540. 

The critics I have read have been so ec¬ 
static in their praise of Carl Pini’s activities 
since he arrived in this country that I ap¬ 
proached this, his debut recording, with 
some humility. I needn’t have bothered. 
Recorded for EMI in Australia its string 
tone is coarse and recorded so close to the 
microphone that you have to turn the 
volume control way down not to be blown 
out of the room. But even after having done 
so the violins sound very edgy and the cello 
is seldom heard, except in solo passages. 
Despite this the playing technically is 
always good and much hard rehearsal must 
have gone into achieving the excellent sense 
of ensemble between all four players. 

But no one will ever convince me that 
Pini’s is the way to play the Debussy 
Quartet. Climaxes, closely approaching 
hysteria, rear up from time to time. High 
solo violin passages are often almost un¬ 


bearably sentimentalised. There is hardly 
ever a moment of relaxation. Everything is 
much too hard-pressed. In fact to my mind 
it is simply just not Debussy. 

This treatment is better suited to Bloch’s 
not very interesting Third String Quartet. 
The work except for a bar here and there, is 
quite without the strongly felt Hebraic 
quality of much of his other work, so often 
redolent of Old Testament. Instead in the 
first three movements you have some well- 
knit commonplaces, admittedly admirably 
played, but to me quite devoid of real 
musical interest. The Finale is a little more 
acceptable since according to the sleeve 
notes, it is based on a 12-tone row developed 
almost strictly diatonically, an unusual 
treatment that, at any rate, keeps the mind 
busy if it seldom involves the emotions. 

★ ★ ★ 

PROKOFIEV — The Two Violin Concertos. 
Nathan Milstein (violin) with in No. 1 the 
Philharmonia Orchestra conducted by 
Carlo Maria Giulini, and in No 2, the 
New Philharmonia Orchestra conducted 
by Rafael Fruhbeck de Burgos. World 
Record Club Stereo S/ 5021. 

If you can enjoy these two concertos 
played with faultless technique if little else 
and issued to members at a budget price, 
this disc is certainly for you. To me they are 
strangely passionless. They sound as if they 
mean little to Milstein, or if they do, he fails 
to register the fact. His approach to these 
two essentially lyrical scores is altogether 
too cool, even mechanical. He gives you too 
much metronomical fiddling better suited 
to the baroque school. Moreover he is oddly 
unobservant of the composer’s expression 
marks, and subtleties of dynamic nuancing 
are almost non-existent, despite obvious 
encouragement from the two different 
conductors who direct the orchestral parts. 

As I said earlier, technically Milstein’s 
playing is exceptional, but emotionally — 
not for me. Try the Isaac Stern recordings 
of these concertos and you will hear what I 
mean. Sound is good average. 


LANTHUR ELECTRONICS 

69 Buchanan Avenue, North Balwyn, Vic 3104 Tel 85 4061 


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LAMP DIMMER BASIC KIT 

We supply 6 amp. triac, diac, pot. with 
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ELECTRONICS Australia, June, 1972 




















five new 
counters 



■ 0-550 MHz 

■ 4 MEASUREMENT MODES 


Digital Electronic Counters 
for versatility and reliability 
without multiple plug-ins. 



Each counter in the series provides 4 meas¬ 
urement modes: Frequency, Period, Multiple 
Period Average and Totalise. An additional 4 
modes are available on some models pro¬ 
viding extended frequency range to 550 MHz, 
Time Interval, Time Interval Average and 
Frequency Ratio. 


8000B Series 


For further Information contact 
Australian Representatives 

JACOBY • 

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SYDNEY 630 7400 BRISBANE 44 4674 
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PERTH 28 5725 


NO LONG WARM-UP DELAY. This is elimin¬ 
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optimum versatility and accuracy in a 
general purpose counter. (A higher stabil¬ 
ity TCXO and a range of oven oscillators are 
options.) 

INPUT SENSITIVITY. Normally 50 mV to 550 
MHz while an optional amplifier will increase 
this to 1 mV with automatic triggering. This 
high sensitivity allows frequency measure¬ 
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signal. 


86 


ELECTRONICS Australia, June, 1972 


































Australian Festival of Music 



N*<:W*y IXHjGRATKJNS 
MOMtNOJS OCCASION CMKrUfe 
THREE FRESCOS 


» SYvKVONY *)0 Of Lit* 
CANOAIAON HHLHIMA ftVNfcLS 


(ONClKIDrOK VOJN 
HALKITD HfcJLS 



VOL. I. ALFRED HILL — Symphony “Joy 
of Life”. 

JAMES PENBERTHY — Cantata on 
Hiroshima Panels. Soloists, the 
Adelaide Singers. Adelaide Philhar¬ 
monic Choir, South Australian Sym¬ 
phony Orchestra conducted by Patrick 
Thomas. 

VOL. 2. NIGEL BUTTERLEY — Ex¬ 
plorations for Piano and Orchestra. Ian 
Farr (piano) with the Sydney Symphony 
Orchestra conducted by Moshe Atzmon. 

JOHN ANTILL — Momentous Occasion 
Overture. Sydney Symphony Orchestra 
conducted by Antill. 

After a long absence from the field of 
classical record production Festival have 
reappeared with a massive issue listed 
above. Moreover more are promised for 
release later this year. It is a joint venture 
with the Commonwealth Assistance to 
Australian Composers, APRA, and the 
Australian Broadcasting Commission. For 
many years now the ABC has prudently 
recorded on tape and disc performances of 
Australian and other music which they 
considered important enough to preserve. 
The result has been the acquisition of a rich 
library to which access has been very 
strictly limited. 

The standard of production is very high 
indeed. The sound is mostly first class, the 
discs have a fine finish and each is 
presented in double-fold covers decorated 
with beautifully reproduced prints of 
Australian paintints. Also featured are the 
photographs of the composers and per¬ 
formers. 

To avoid confusion I shall take them in 
numerical order though it will soon be 
apparent that that is not the way in which 
my interest lies. In Vol. 1 Alfred Hill’s 
symphony, “Joy of Life”, shows almost 
every influence of the 19th century German 
and other Central European romantics but 
despite this the first second and third 
movements still .have much innocent 
charm. But in the choral finale — ‘‘Gloria in 
Excelsis Deo” — Hill tried to be grand but 
succeeded only in being banal, a kind of 
poor man’s Liza Lehmann. This was not 
Hill’s line of country at all. His small talent 
was better suited to more modest en¬ 
deavours. Both the playing and singing 
offer much to enjoy and the sound is first 
rate. 

James Penberthy’s “Cantata on 
Hiroshima Panels” is much sterner stuff 
though still well within the range of popular 
appreciation. Though conventional 
melodically and harmonically it conveys 


CLIVE DOUGLAS — Three Frescos. 
Sydney Symphony Orchestra conducted 
by Moshe Atzon. 

VOL. 3. FELIX WERDER — Concerto for 
Violin. Leonard Dommett (violin) and 
the Melbourne Symphony Orchestra 
conducted by Fritz Rieger. 

MARGARET SUTHERLAND — Haunted 
Hills. Melbourne Symphony Orchestra 
conducted by John Hopkins. 

VOL. 4. RICHARD MEALE — Clouds Now 
and Then. Homage to Garcia Lorca. 
West Australian Symphony Orchestra 
conducted by John Hopkins. 

RAYMOND HANSON — Fern Hill. Molly 
McGurk (soprano) with the West 

eloquently the composer’s deep sense of 
outrage at the Hiroshima nuclear slaughter. 
His expressive vocal line has very 
professionally scored orchestral ac¬ 
companiment. Again the playing, singing 
and recording are of a high standard. 

In Vol. 2 those who know their way around 
contemporary music should find no dif¬ 
ficulty with Nigel Butterley’s “Ex¬ 
plorations” the first time through. Indeed, 
to me, it sounded more impressive at first 
hearing than at subsequent repetitions. 
There is nothing way-out about the com¬ 
position. It is very expertly put together in 
an idiom that even today (it was first 
performed to celebrate the Captain Cook Bi- 
Centenary Celebrations in 1970) already 
sounds a little dated. It certainly has an 
occasional impressive, even moving 
sequence, but on the whole I prefer But- 
terley in his more pious moods. The SSO 
under Moshe Atzmon provide a well 
balanced background to Ian Farr’s splendid 
performance of the solo piano part. In the 
following notices you can take it for granted 
that unless I specify otherwise the 
engineering is always of a very high quality. 

John Antill’s “Momentous Occasion 
Overture” was, I felt, composed in a mood 
of dogged high spirits — come what may. It 
was, however, eminently suited to the oc¬ 
casion which it celebrated, the 10th an¬ 
niversary of the ABC’s Youth Concert 
series. Antill may not nave very much to 
say here but he communicates everything 
in a very civilised language. 

In his “Three Frescos” Clive Douglas’s 
use of dissonance seldom disguises the 
conventionality of his musical thoughts. The 
music is all very worthy, at times warmly 
melodious and always colourfully or¬ 
chestrated. One might describe him, with 
some reservations, as an Australian 
Respighi. The SSO again plays accurately 
and expressively, the Antill work under the 
baton of the composer, the Douglas under 


Australian Symphony Orchestra con¬ 
ducted by Sir Bernard Heinze. 

GEORGE DREYFUS — Jingles. West 
Australian Symphony Orchestra con¬ 
ducted by Sir Bernard Heinze. 

VOL. 5. IAN FARR — Sonata for Cello and 
Piano. Gregory Elmaloglou (cello) and 
Nigel Butterley (piano). 

DONALD HILLIER — Variations on a 
Theme of Larry Sitsky. Carl Pini (violin) 
and Beryl Potter (piano). 

LARRY SITSKY — Sonata for Solo Flute. 

Margaret Crawford (flute). 

PETER SCULTHORPE — Landscape for 
Piano with feedback and pre-recorded 
tape. David Bollard (piano). 

Atzmon’s. 

Felix Werder’s Violin Concerto is a com¬ 
pact work unrelenting in its logic but with 
some fine lyrical moments. Werder is also, 
of course, a critic of no mean — and perhaps 
sometimes very mean — perspicacity. His 
highly amusing sleeve comments on the 
concerto as a musical form would be well 
worth reprinting here except for the warn¬ 
ing that they are the author’s copyright. 
A pity because, unlike his concerto, there’s 
a laugh in every line. Leonard Dommett 
gives an entirely satisfactory account of the 
solo violin part and Fritz Rieger’s con¬ 
ducting of the MSO advertises his complete 
sympathy with this type of exercise. 

The coupling, Margaret Sutherland’s 
“Haunted Hills”, offers a not altogether 
suitable contrast to the Werder concerto. I 
don’t think I would have chosen it as 
representative of Miss Sutherland at her 
best though for the most part it retains an 
air of freshness that remains, despite 
familiarity with the score. It is in two parts 
and it is in the second part that the com¬ 
poser’s invention seems to lag to an extent 
that makes the conductor, John Hopkins, 
appear to have some difficulty in sustaining 
the scherzando instructions given by the 
composer. However when one remembers 
that Miss Sutherland was born in 1897, only 
7 years after the late deeply revered Alfred 
Hill, the originality of her talent is much to 
be admired. 

If I had to choose one out of the five, Vol. 4 
would have my unqualified preference. It 
was the first one I played and is still the one 
to which I return most frequently. On the 
first band, in “Clouds Now and Then” you 
have Richard Meale in a mood poetically 
evocative of the title. Listening to it, it is not 
difficult to imagine yourself lying on your 
back in scented grass idly watching drifting 
clouds. Sometimes you think of them, 
sometimes of other things, as Meale might 
have intended you to do in his eclectic 


ELECTRONICS Australia, June, 1972 87 












IMPORTED COMPONENTS 

P.O. BOX 1683P 


ALL PRICES 
INCLUDE 

TAX AND POSTAGE 


SPECIALS 


AC 126 

.85 

AC 187 / 188 

2.00 

AY 1101 

.28 

AY 1110 

.99 

AY 1112 

,51 

AY 1115 

.46 

BA100 

.36 

BC207 

.59 

BC209 

.70 

BF115 

.78 

EM402 

.23 

EM404 

.26 

EM 406 

.34 

EM408 

.42 

OA90 

.29 

OA91 

.30 

OA95 

.35 

OA202 

.60 

ORP12 

.75 

SP1460 

3.00 

SE1001 

.27 

SE4002 

.50 

SE4010 

.57 

ST2 

1.10 

40669 

3.10 

2N3053 

1.57 

2N3055 

1.40 

2N3565 

.42 

2N3568 

.67 

2N3569 

.71 

2N3638 

.57 

2N3638A 

.75 

2N3642 

.81 

2N3644 

.78 

2N3645 

.88 

2N3693 

.26 

2N3819 

. .77 

1N645 

.84 

1N914 

.51 

IN3491 + R 

1.75 

IN3492 + R 

1.83 

1N3493 + R 

2.36 

IN3660 T- R 

1.99 

2N174 

6.09 

2N217 

1.24 

2N277 

2.32 

2N301 

3.06 

2N301A 

4.23 

2N406 

1.01 

2N417 

1.77 

2N441 

1.80 

2N443 

3.22 

2N456A 

4.20 

2N489B 

14.76 

2N591 

2.61 

2N649 

2.12 

2N696 

1.13 

2N697 

2.34 

2N706A 

1.80 

2N930 

1.80 

2N1038 

3.92 

2N1046 

17.94 

2N1073B 

7.59 

2N1302 

1.01 

2N1303 

1.01 

2N1305 

1.13 

2N1306 

1.32 

2N1307 

1.32 

2N1308 

1.64 

2N1309 

1.64 

2N1546 

- -5.85 

2N1639 

1.39 

2N1908 

27.74 

2N2102 

3.17 

2N2147 

5.04 

2N2160 

2.40 

2N2188 

2.79 

2N2270 

2.40 

2N2646 

2.19. 

2N2647 

3.15' 

2N2669 

6.53 

2N2926 

2.25 

2N3005 

5.32 

2N3054 

1.80 

2N3525 

3.70 

2N3563 

.90 

2N3564 

1.08 


2N3566 

1.01 

2N3567 

1.08 

2N3691 

.86 

2N3692 

.90 

2N3694 

.90 

2N3702 

1.01 

2N3703 

.96 

2N3704 

1.77 

2N3705 

1.73 

2N3706 

1.65 

2N3707 

1.14 

2N3708 

.80 

2N3716 

5.30 

2N3731 

3.17 

2N3790 

11.25 

2N4121 

1.04 

2N4250 

1.17 

2N4354 

1.28 

2N4355 

1.65 

2N4356 

1.65 

2SB186 

1.50 

2SB407 

3.30 

2SB474 

3.30 

2SF28 

5.60 

3N140 

2.97 

3N141 

2.95 

AA119 

.36 

AC 107 

2.28 

AC 125 

.96 

AC 128 

1.05 

AC 132 

1.01 

AC 172 

1.20 

AD 149 

2.45 

AD161 / 162 

4.32 

AN 1102 

.68 

AN 1103 

.60 

AN 1104 

.60 

AN 1105 

.60 

AN 2001 

.45 

AN 7102 

.90 

AN 7105 

.68 

AS 147 

.80 

AS 148 

.76 

AS 208 

1.68 

AS301 

.91 

AS 306 

.96 

AS 307 

.96 

AS 308 

.99 

AS310 

1.12 

AS311 

1.10 

AS312 

1.10 

AS313 

1.08 

ASY73 

1.66 

ASY76 

2.10 

ASY77 

1.80 

AS216 

3.03 

AS217 

2.59 

AS218 

2.91 

AS 220 

.98 

AS221 

2.16 

AT316 

.68 

AT318 

.68 

AT319 

.69 

AT322 

.63 

AT323 

.68 

AT 3 24 

.68 

AT325 

.83 

AT331 

.92 

AT337 

.69 

AT338 

.70 

AT341 

.70 

AT350 

1.14 

ATI 138 

2.66 

AX 1101 

1.53 

AX 1103 

1.70 

AX 1104 

1.86 

AX 1108 

1.86 

AX 1127 

1.50 

AX 1130 

1.50 

AX 1131 

1.77 

AX 1132 

1.50 

AX 1142 

1.20 

AX 1143 

1.58 

AX 1144 

1.44 

AX 1166 

1.37 

AX 6168 

1.98 

AY 1102 

1.04 

AY 1108 

1.65 

AY 1113 

.69 

AY 1119 

.60 


MELBOURNE 3001 


AY6108 

1.65 

AY 6109 

1.65 

AY8108(8103) 

3.75 

AY 8109(8104) 

3.00 

AY8112 

6.75 

AY8135 

5.40 

BA102 

1.46 

BA114 

.39 

BC107 

.83 

BC108 

.76 

BC109 

.91 

BC147 

.76 

BC148 

.68 

BC149 

.79 

BC157 

.89 

BC158 

.76 

BC159 

.89 

BC177 

.91 

BC178 

.84 

BC179 

.92 

BC208 

.63 

BC212 

2.00 

BCY10 

2.59 

BCY11 

3.24 

BCY12 

3.14 

BCY39 

5.19 

BCY71 

2.05 

BCZ210 

1.95 

BCZ211 

2.37 

BCZ212 

2.16 

BD139 

3.67 

BD140 

3.90 

BDY20 

2.63 

BDY38 + 

2.62 

BF145 

.64 

BF173 

1.14 

BF177 

1.63 

BF178 

1.80 

BF179 

2.04 

BF18 

.72 

BF185 

.72 

BF194 

.67 

BF200 

1.32 

BFY51 

5.19 

BSX19 

2.16 

BSX20 

2.39 

BT100A / 500R 

3.00 

BT101 / 500 

5.40 

BTY79 / 100R 

2.70 

BTY79/300R 

3.45 

BTY79 / 500R 

5.19 

BY 127/ 800 

.78 

BYX21L/200R 

1.35 

BYX38/300 + R 

1.32 

BYX38 / 600 + R 

1.62 

BYX38 / 900 + R 

2.08 

BYX38 / 1200 + R 

3.03 

BYX39/600 + R 

3.14 

BYX39 / 800 + R 

3.88 

BYX39 / 1000 -F R 

4.53 

B2X70Scvies 

1.35 

B2Y88C303toCl 1 

.65 

B2Y88C12toC30 

.82 

BZY95 Scvies 

2.16 

BZY96 Scvies 

2.16 

BZZ15to29 

1.95 

C20D + 

6.60 

C106 / Y1 

2.10 

C122D 

3.78 

D13TI 

1.95 

DTG110B 

6.96 

DTG1010 

15.16 

EM410 

1.40 

FLV100 

3.30 

FPT100 

1.80 

H35 

8.07 

MB1 

2.03 

MB3 

2.65 

MB6 

3.40 

MB8 

4.30 

MJE2955 

4.55 

MJE3055 

3.06 

OA5 

.65 

OA10 

.87 

OA47 

.65 

OC20 

6.38 

OC22 

3.03 

OC23 

3.80 

OC24 

3.45 

OC44N 

1.11 


OC45N 

1.11 

OC74N 

.96 

0041 

2.60 

OC201 

3.80 

OC202 

3.70 

OCP70 

2.60 

OCP71 

4.32 

ORP60 

1.75 

PA40 

4.83 

PB40 

7.26 

SC45D 

11.10 

SC50D 

13.00 

SE2001 

.98 

SE2002 

1.20 

SE3001 

1.12 

SE5001 

2.10 

SE5002 

2.10 

SE5003 

2.48 

SE5020 

4.05 

SE5023 

3.15 

SE5025 

1.35 

T1 / 40 / A2 

3.30 

T13027 

2.61 

TIC44 

1.68 

TIC45 

1.88 

TIC46 

2.05 

TIC47 

2.30 

TIP31A 

2.10 

TIP32A 

2.70 

TIP33A 

2.98 

TIS34 

2.46 

TIS43 

2.36 

40360 

2.48 

40361 

2.70 

40407 

2.52 

40408 

2.98 

40409 

3.15 

40410 

3.30 

40411 

7.00 

FETS 

MPF102 

1.00 

MPF104 

1.10 

MPF105 

1.50 

MPF121 

1.50 

2N3820 

4.55 

2N4360 

1.55 

2N4889 

2.50 

2N5245 

2.50 

2N5485 

1.50 

2N5486 

1.60 

I.C.'S 

uA703 

2.25 

uA709 

1.50 

uA710 

1.65 

uA716 

5.60 

uA723 

3.80 

uA739 

5.00 

uA741 

2.25 

FUL900 

1.20 

FUL914 

1.10 

FUL923 

2.25 

LM301A 

2.25 

LM305 

7.27 

LM309K 

4.80 

LM370 

6.50 

LM372 

5.50 

MC1303L 

5.00 

SN7400series exstock P.O.A. 

TAA300 

4.30 

TAA570 

4.20 

TAA840 

5.40 

TA10A 

8.75 

TA20 

26.00 

TA25 

32.00 

TA50 

39.00 

TRANSISTORS 

BC182L 

150 

TT800 

1.95 

TT801 

1.95 

3N81 

6.40 

TIL209(LED) 

2.40 

40362 

3.10 


88 ELECTRONICS Australia, June, 1972 










mood. Some give rain — there is a little 
stormy passage — others just pattern the 
sky. The playing of the West Australian 
Orchestra is purposeful, John Hopkins’ 
conducting shows complete understanding 
of and devotion to this lovely sound. 

Homage to Garcia Lorca is probably, in 
the widest sense of the word, Meale’s best 
known work and Sir Bernard Heinze leads 
the WA Orchestra through it with particular 
attention to the music’s moving poignancy. 
But I felt that he was not as well served by 
the WA strings as he might have been. Their 
tone tends to wiriness, though this might be 
due to the engineering. But even this does 
not spoil the overwhelming effect of the 
great final climax. Raymond Hanson’s 
Fern Hill is a setting of a Dylan Thomas 
poem, the text of which would have been 
welcome since Miss McGurk’s diction is so 
unclear that only an occasional word can be 
understood. And despite Heinze’s paternal 
handling of the colourfully scored or¬ 
chestral part her soprano sometimes 
sounds a little backward. Otherwise it is 
clear, fresh and accurately pitched. 

That irrepressible prankster George 
Dreyfus is again elegant and witty in his 
Jingles. In this suite of parodies of all kinds 
of music, classical and popular, he is at his 
wittiest best. Listening to them I was 
constantly reminded of Max Beerbohm’s 
similarly elegant exercise, but in the 
literary medium, in his Savanorola Brown. 
It is a piece it will take me long to tire of and 
Heinze relishes its humour as the. good 
raconteur he is. There is no rib-digging. He 
lets every bar speak sparklingly Tor itself. 

The outstanding piece in Vol. 5 is 
Sculthorpe’s Landscape, in which the solo 
pianist improvises at times on the 
predetermined sounds on a pre-recorded 
tape. Sculthorpe struck gold, in every sense 
of the word, with his Sun Music series and in 
this piece, too, I, at any rate, could again 
feel the same sun glaring from a tape that 
shudders, clicks and glitters. David 
Bollard’s improvisations occasionally 
sound a little too mellifluous against 
Sculthorpe’s background though there are 
passages when the blending of the two 
minds seems complete. I wonder if these 
were some of the pre-determined bits? 
Sculthorpe is an inexhaustible explorer into 
musical “effects” and some displayed here 
are ingenious and, to my ear, original. An 
interesting short piece that will bear much 
repetition. 

Margaret Crawford offers some delicious 
flute playing in Sitsky’s unaccompanied 
Flute Sonata. But was it necessary to record 
so close that her breathing often becomes 
part of the entertainment? But this apart, 
she has a lovely reedy tone in the low 
register and unforced brilliance in the 
higher. Sitsky’s work, an earlyish one, 
shows some allegiance to Honegger’s short 
piece for solo flute, The Goat ; though where 
the Honegger piece is just long enough, 
Sitsky’s, without Honegger’s sense of 
humour, seems to me to go on far too long. 

Ian Farr’s Sonata for Cello and Piano is a 
fashionably fragmented exercise, typical of 
those heard, usually once only, at avant 
garde music festivals. It is, however, 
brilliantly played by Elmaloglou and 
Butterley. 

Hollier’s set of variations shows con¬ 
siderable technical resources by the 
composer and the performers, Carl Pini and 
Beryl Potter. c £ 


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3 motors, 6-head function, 3 speeds. Sony’s TC-730 is a.... 


Modern Marvel 



un¬ 
its 3 
And the 


This is the greatest machine 
has evolved from Sony’s long line 
of great open reel recorders. It 
the smoothest tape transport yet 
achieved. Wow and flutter are an 
credible 0.06% at 7Vi 2 ips. due to 
remarkable eddy current motors, 
range of features! Here are some. 

Six-head function for recording and playback both 
ways permits tape/source monitoring while recording. 

Auto-reverse system with sensing foil automatically re¬ 
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provided with choice of CONTINUOUS REVERSE, REVERSE or 
REVERSE OFF. Automatic positioning pinch roller symmetrically posi¬ 
tioned beneath the capstan assures extremely precise tape transport. 

Perfect auto shut-off—Motor stops and pinch roller is detached when tape 
fully unwinds or accidentally breaks. Sleeping switch stops tape and turns off 
power automatically on completion of tape. Scrape filter highly effective in cutting 
down modulation noise and tape hiss. Built-in monitor speaker (5W x 2 power output) with detachable reflector 
provide better monitoring performance. High-quality all silicon transistor circuitry including OTL (output trans¬ 
formerless), ITL (input transformerless) circuits. 40W (20W x 2) power output through a power amplifier. Capable 
of mike and auxiliary input mixing without external mixer. Equipped with public address facility. Switch for echo 
effect and sound-on-sound recording. Regulated power supply incorporated in deck section. Two headphone jacks 
— one for monitoring and the other for private listening with control for volume and tone as desired. 3 tape 
speeds; four-digit tape counter; either vertical or horizontal operation; built-in reel locks; large, easy-to-read level 
meters; tape selector; separate bass and treble tone controls; feather-touch piano-key operation. 



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ELECTRONICS Australia, June, 1972 


90 













VARIETY FARE 

REVIEWS OF OTHER RECORDINGS 


Devotional Recordings 

IT’S REAL. Dale Evans, with orchestra and 
chorus conducted by Anita Kerr. Stereo, 
Word WST-8546-LP (From Sacred 
Productions Aust, 181 Clarence St, 
Sydney and other capitals). 

Dale Evans and her husband Roy Rogers 
are well known for their leadership among 
the evangelical community in Hollywood. In 
presenting this album Dale Evans says: 
“Our Lord . . . has proved himself to me 
over and over again, through very deep 
waters.” The titles: 

Standin’ In The Need Of Prayer — Old 
Time Religion — When I Met My Saviour — 
Every Time I Feel The Spirit — One More 
River — Ezekiel Saw The Wheel — It’s Real 
— Deep River — Oh Saviour — Nobody 
Knows The Trouble — Onward Christian 
Soldiers — Joshua Fit The Battle. 

An experienced Gospel vocalist, Dale 
Evans is skilfully backed by Anita Kerr and 
her music, providing variety and avoiding 
any risk of the solo voice becoming 
monotonous. This one should have a ready 
appeal in Gospel circles. (W.N.W.). 

★ ★ ★ 

EXCERPTS FROM A CHORAL CON¬ 
CERT. The Choir of the Peace Memorial 
Church, Castle Hill, Sydney. Conductor 
Fred Grice; Soloist Elaine Abrahams; 
Organist Bev. Shadlow; Pianiste 
Elizabeth Cannon. Parker, Mono PR-004. 

In a few short years Castle Hill has 
changed from a quiet farming community 
on Sydney’s western fringe to a thriving 
suburb. During the same period, a tiny 
Baptist cause has built and outgrown one 
church and has just opened a fine new build¬ 
ing to accommodate 500 worshippers. 

The vitality of this young church is 
reflected in the choir which features in this 
LP. As a suburban church choir it is well 
above average. As a recording group, it has 
potential but the female voices in particular 
need more discipline to achieve the ultimate 
roundness and the polish that distinguishes 
a “professional” group from enthusiastic 
choristers. Evaluated at this level, you may 
find the program to your liking.: 

Gloria — The Lord’s Prayer — Amen — 
Lead Me, Lord — King All Glorious — This 
Little Light — The Lord Is My Light — 
Jacob’s Ladder — Jesu, Joy Of Man’s 
Desiring — My Shepherd — Peace In The 
Valley — Hallelujah Chorus. 

In terms of quality, the general balance is 
good, with just a trace of edginess on a wide- 


range system. (From Parker Recordings, 9 
Carmel Place, Winston Hills, 2153. Price 
$3.99 plus 50c pack and postage.) (W.N.W.). 

★ ★ ★ 

HIS NAME IS WONDERFUL. Norma 
Zimmer & Jim Roberts. Stereo, Word 
WST-8541-LP. (From Sacred Produc¬ 
tions Aust., 181 Clarence St, Sydney and 
other capitals). 

Per medium of Lawrence Welk and 
network television, and also the Billy 
Graham crusades, Norma Zimmer and Jim 
Roberts are well known to American 
audiences. With duet arrangements of well 
known hymns, their album could be quite 
commonplace. It isn’t, because of excellent 
orchestral support, a polished performance 
and a feeling of personal conviction and 
involvement. 

The tracks: His Name Is Wonderful — 
Every Moment Of Every Day — He Lifted 
Me — When I Kneel To Pray — I Would Be 
Like Jesus — Sweet, Sweet Spirit — His 
Gentle Look — Take Up Thy Cross — He 
Touched Me — Beyond The Sunset. 

I noted a slight surface prickle on side 2 of 
this American pressing but the quality and 
balance is otherwise first class. I think 
you’ll enjoy this one. Recommended. 
(W.N.W.). 

★ ★ ★ 

NEGRO SPIRITUALS. George Browne, 
Martin Lawrence, Isabelle Lucas, 
Geoffrey Taylor and the Linden Singers. 
World Record Club stereo S / 2005. 

Old time WRC members will recognise 
this disc, which has been reissued 
periodically (presumably because of 
demand by new members) since it first 
appeared in the Club catalogue more than 
10 years ago. I have heard it described as 
“the finest negro spiritual record ever 
made” or “a beaut disc” by enthusiastic 
owners. The fact that the recording was 
made in London, and that there is not a 
single negro in the group, might surprise 
some of these people. Yet this is probably 
the reason for the disc’s success. It is a 
restrained performance, without any of the 
emotional and vocal excesses which 
characterise so many performances by 
negroes in material of this kind. It is, in 
fact, very much a white man’s view of negro 
spirituals — and will appeal as such to the 
listener. 

The contents are pretty predictable: 
Jericho — Nobody Knows — Little David — 
Sometimes I Feel — Lily of the Valley — 
Gospel Train — He’s Got the Whole World — 
Shadrak — Go Down Moses — Deep River 


— Sweet Little Jesus Boy — Heaven — 
Swing Low — Standing in the Need of 
Prayer. The sound is definitely dated, but is 
acceptably clean. (H.A.T.). 

★ ★ ★ 

ROCK GOSPEL. TTie Key To The Kingdom. 
Various Artists. Stereo, Tamla Motown 
(EMI) STMLO-10080. 

If you like Gospel rock, Gospel happen¬ 
ings and that kind of sound, this album may 
well be for you, particularly as it contains 
tracks by a variety of artists: 

Hey Lordy (Bobby Taylor) — Sinner Man 
(Valerie Simpson) — May His Love Shine 
(The Supremes) — God Bless The Child 
(Blinky) — Bridge Over Troubled Water 
(Jackson 5) — As Heavy As Jesus (Stoney & 
Meatloaf) — What A Friend We Have 
(Impact of Brass, Joe Hinton) — Jesus Is 
The Key (Ken Christy & The Sunday 
People) — Tliere Is A God (Valerie Simp¬ 
son) — God Is Love (Marvin Gaye) — How 
Great Thou Art (Gladys Knight & The 
Pips). 

Some of the tracks are more restrained 
than others but this fact would not be 
enough to commend the record to me, 
personally. However, if this kind of music 
turns you on, there is no need for apprehen¬ 
sion about the ability of the performers or 
the quality of the recording. (W.N.W.). 

"Instrumental, Vocal 
and Humour . . . 

RIMSKY-KORSAKOV’S GREATEST 
HITS. Various artists and orchestras. 
RCA Red Seal stereo LSC-5012. 
RAVEL’S GREATEST HITS. Various 
artists and orchestras. RCA Red Seal 
stereo LSC-5002. 

Here are two of the latest releases of 
tracks from earlier RCA discs in the 
company’s “Greatest Hits . . .” series, 
containing popular classics and excerpts 
from longer works of the most famous 
composers. Some tracks are fairly ob¬ 
viously a bit long in the tooth, but most seem 
to be of quite recent origin, with good 
modern sound. The usual or¬ 
chestra / conductor combinations of the 
past and present RCA catalogue are mostly 
featured — Boston Pops / Fiedler; The 
Philadelphia / Ormandy; Chicago Sym¬ 
phony / Reiner and Martinon; RCA Or- 



Reviews in this section ate by Neville Williams (W.N.W.), Harry Tyrer (H.A.T.), Leo 
Simpson (L.D.S.) and Gil Wahlquist (G.W.). 


ELECTRONICS Australia, June, 1972 


91 















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chestra Kondrashin; Boston Sym¬ 
phony Munch; London Symphony Previn 
— and with such performers, the results 
could hardly be less than satisfactory, and 
some of them can be rated considerably 
higher than this, e.g., the excerpts from 
“Scheherazazade” in the Rimsky-Korsakov 
selection. 

The Rimsky-Korsakov disc has: Flight of 
the Bumble Bee — The Young Prince and 
the Young Princess, Festival of Bagdad, 
The Ship Goes to Pieces on a Rock (all from 
“Scheherazade”) — Procession of the 
Nobles from “Mlada” — Song of India — 
Bridal Procession from “Le Coq D’Or” — 
Excerpts from “Capriccio Espagnol” — 
Tsar Saltan March. The sound in the “Song 
of India” track is below standard, and has 
noticeable tape hiss. On the Ravel disc: 
Bolero — La Valse — Daphnis and Chloe — 
Pavane for a Dead Princess — Rigadon 
from “Le Tom beau de Couperin” — 
Alborado del Gracioso — Feria from 
“Rapsodie Espagnole”. (H.A.T.). 

★ ★ ★ 

THE GREAT CANTATAS (J. S. BACH) 
VOL 10. Soloists with the Heinrich Schutz 
Chorale of Heilbronn and the Pforzheim 
Chamber Orchestra conducted by Fritz 
Werner. 

This series has been running in the World 
Record Club catalogue for some months, 
and we draw it to the attention of readers as 
it is the type of series which continues to be 
available after the issue date. In fact, this 
particular disc is an excellent one to start< 
with, as it contains the very popular can¬ 
tatas “Ach Wie Fluchtig” and “Nun Komm, 
Der Heiden Heiland”. The disc is completed 
by “Her Gott, Dich Loben Alle Wir”. 

The singing throughout is of a good 
standard rather than outstanding, and the 
whole thing engenders an atmosphere oT 
earnest endeavour, rather than inspiration. 
Nevertheless, with great music such as this, 
a competent performance is sufficient to 
allow the music to speak for itself. I 
thoroughly enjoyed listening to it, and I am 
sure most people will be affected the same 
way, unless they have been influenced 
already by some favourite performance 
they already know. The sound is good, and 
the stereo normal. (HAT.) 

★ ★ ★ 

CLASSICAL TOP TEN. Various artists and 
orchestras. Philips “Universo” series 
(Phonogram Recordings) stereo 6833 
040. 

One could perhaps take issue with the 
person who named this disc about the ac¬ 
curacy of the title, but nevertheless it does 
contain an attractive selection of classical 
tunes played by top artists and orchestra, 
including the English Chamber Orchestra, 
London Symphony Orchestra, Lamoureux 
Concert Orchestra and the Concertgebouw 
Orchestra. 

The tunes are: Symphony No 40, first 
movement (Mozart) — Air on the G String 
(Bach) — Baderinie from Suite No 2 (Bach) 
— Finale from Serenade for Wind In¬ 
struments (Dvorak) — Symphony No 9, 
excerpt from Finale (Beethoven) — Sabre 
Dance (Khatchaturian) — Concerto de 
Aranjuez, Adagio (Rodrigo) — Prelude in C 
sharp minor (Rachmaninov) — Adagio in G 
minor (Albinoni) — Danse Macabre (Saint- 
Saens). 


ELECTRONICS Australia, June, 1972 


The standard of performance is high 
all through, and the sound is satisfactory. 
(HAT). 

★ ★ ★ 

THE FOUR SEASONS — Vivaldi. Henryk 
Szeryng (conductor and soloist) with the 
English Chamber Orchestra. Philips 
“Universo” Series (Phonogram 
Recordings) stereo 6580 002. 

There is certainly no shortage of accept¬ 
able recordings of this popular work 
throughout the whole spectrum of retail 
prices. However, this particular version 
would be worth attention at any price, 
featuring as it does such an eminent co¬ 
operation of soloist and orchestra.. It 
becomes particularly interesting when 
released on the Philips medium price 
“Universo” label. 

This is a thoroughly enjoyable per¬ 
formance, splendidly played, and very well 
recorded. I should, however, point out that 
Szeryng”s strong playing tends to dominate 
the work to some extent, so that it seems 
much more like a work for solo violin with 
orchestral accompaniment than is normal. 
This has been accentuated by the 
prominence the recording engineer has 
given to the solo violin. (H A T.). 

★ ★ ★ 

SEMPRINI GOLDEN ALBUM. Semprini 
and his Orchestra. Studio 2 Stereo (EMI) 
TWO 358. 

Semprini is more of an entertainer than a 
serious musician, and it happens that his 
brand of entertainment involves light 
classical music. Having accepted this, one 
is able to adjust one’s thinking to the value 
of his discs as entertainment, rather than 
trying to judge them on their musical 
merits. Nobody is going to pretend that his 
version of the Adagio from Beethoven’s 
“Moonlight” Sonata as presented here will 
appeal to devotees of performers such as 
Rubinstein, Kempff, Barenboim and 
Richter. Nevertheless, there is a large body 
of listeners who enjoy the Semprini recipe 
of light classics arranged for piano and 
orchestra. And these folk will appreciate 
the attractive program Semprini has 
devised here, comprising: Gold and Silver 
Waltz (Lehar) — Traumerei (Schumann) — 
Chanson de Matin (Elgar) — Adagio from 
“Moonlight” Sonata (Beethoven) — Song of 
India (Rimsky-Korsakov) — Prelude in C 
Sharp minor (Rachmaninov)—Sheep May 
Safely Graze (Bach) — Rustle of Spring 
(Sinding) — Skaters’ Waltz (Waldteufel) — 
Claire de Lune (Debussy) — La Golondrina 
— Cradle Song (Brahms) — Meditation 
(Massenet). Tuneful, undemanding, nicely 
played, it makes good entertainment for 
those who do not take their classics too 
seriously. The Studio 2 sound is good, and 
the stereo is well spread. (H A T.). 

★ ★ ★ 

FOR ALL WE KNOW. Andre Kostelanetz 
and his orchestra. CBS stereo SBP 
233994. 

If record buyers bought on titles alone 
then this disc would be a best-seller because 
all the titles are currently very popular. But 
the musical arrangements on the disc are 
lacklustre and the sound quality is poor, 
especially for a full price disc. Frankly, 
there is little to commend it. 

For those who are still interested, the 
tracks are: For All We Know — Put Your 


92 







Hand In The Hand — I Don’t Know How To 
Love Him — If — Pieces Of Dreams — 
Lolita — Bridge Over Troubled Water — 
Someone Who Cares — I Think Of You — 
Love’s Lines, Angles And Rhymes — Losing 
My Mind. (L.D.S.). 

★ ★ ★ 

THE GOLDEN AGE OF ENGLISH LUTE. 

Julian Bream, lute. Stereo, RCA Red 

Seal Victor LSC-3196. 

Before the guitar was introduced into 
England by the Spaniards in the 16 th cen¬ 
tury, the lute was the stringed instrument 
commonly used in polite society as an ac¬ 
companiment for voice, and as a solo in¬ 
strument. The selections presented here are 
by some of the best known composers of lute 
music: Two Almaines (R. Johnson) — 
Fantasia (J. Johnson) — Walsingham 
(Cutting) — Mignarda (Dowland) — 
Almaine (Cutting) — Galliard (Rosseter) — 
Greensleeves (Cutting) — Galliard 
(Dowland) — Pavan (Morley) — Carman’s 
Whistle (R. Johnson) — Pavan (Bulman) — 
Monsieur’s Almaine (Batchelar) — Pavan 
(Holborne) — Battel Galliard (Dowland) — 
Galliard (Holborne).Played by a performer 
of the standard of Julian Bream, this makes 
very pleasant listening. Space will not allow 
any detailed discussion, but if you like 
medieval music, I do suggest it is worth 
your while to ask your retailer to let you 
hear a track or two. 

I suggest any of the pieces by Dowland or 
Cutting for sampling, and if you thought you 
knew the “Greensleeves” tune, listen to 
what Cutting makes of this familiar melody. 
The quality of the recording is first class, 
bright, clean and commendably free of tape 
hiss, which often becomes noticeable in solo 
recitals. (H.A.T.). 

★ ★ ★ 

MUSICA DA NOITE. Rogero’s Brazilian 
Brass. Astor 4D series stereo SPLP 
1371. 

Rogero’s Brazilian Brass consists of three 
trumpeters backed by a Latin-American 
rhythm section. As such they turn out music 
in a workmanlike manner although their 
arrangements are not startlingly original. 
Sound quality is standard and stereo spread 
is wide and even. 

There are twelve tracks, with English and 
Spanish titles: Morning In The City — A 
Little Night Music — Knock Three Times — 
Lost In The Night — Dance Of The Hours — 
Brasilia 71 — Brazilian Women — Peter 
And The Wolf — Pushbike Song — 
Habanera — Rose Garden — Sugar Sugar. 
(L.D.S.). 

★ ★ ★ 

I LOVE PARIS. The Melachrino Strings and 

Orchestra, with the Trio Musette de 

Paris. Stereo RCA Camden CAS-2507. 

The familiar sound of the Melachrino 
strings is supplemented here by the 
pleasant accordeon sounds of the Trio 
Musette de Paris, who provide the Con¬ 
tinental touch to this collection of popular 
Parisian songs. The Melachrino Strings 
perform in their usual competent fashion, 
and the music has been skilfully arranged 
by Melachrino himself — and is there 
anybody who can surpass him in this? 

There are only nine tracks on the disc, in 
line with RCA’s apparent policy of reducing 
the playing time of their LP discs. With less 


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than 14 minutes playing time on side 1 and a 
very ungenerous IIV 2 minutes on side two, 
one wonders how far they can go with this 
policy. The tracks are: I Love Paris — April 
in Paris — La Seine — Song of Moulin Rouge 

— J’Attendrai — C’est Si Bon — Clopin 
Clopant — Poor People of Paris — La Mer. 
The sound quality is of good standard. 
(H.A.T.) 

★ ★ ★ 

ALL-TIME GUITAR HITS EXOTIC 
GUITARS. Interfusion stereo SITFL- 
934446. Distributed by Festival Records 
Pty Ltd. 

Just who the Exotic Guitars are played by 
is not revealed on the record which 
originates in the USA but they are a skilful 
group playing in much the same style as the 
Ventures. Recording quality and stereo 
spread are good throughout so you can buy 
without hesitation. 

Twelve tracks are featured: Memphis — 
Maria Elena — Apache — Wildwood Flower 

— Rebel Rouser — The Enchanted Sea — 
Classical Gas — Exotic Guitar Boogie — 
Sleep Walk — Walk, Don’t Run — The 
James Bond Theme — Raunchy. (L.D.S.) 


MY HEART REMINDS ME. Wilbur Kentwell 

playing the 3*manual Conn Theatre Organ. 

Stereo, RCA Victor sl-101978. 

I haven’t responded all that warmly to some 
of Wilbur Kentwell’s recent albums but I have 
no such reservations about this one. It’s a 
beauty and one that will stand comparison to 
almost any recording I have ever heard of an 
electronic organ. In fact, it embodies the big 
sound and the playing techniques commonly 
associated with the pipe instruments. 

The organ itself is the big 3-manual Theatre 
Conn, feeding into pipe loudspeakers, as well 
as the usual fixed and rotating sound-field 
types. The sound is at the one time full and 
brilliant — and completely clean. 

The generously timed program also will 
have a lot of appeal, being made up of popular 
modern themes which have their roots in the 
classics: Till The End Of Time — Chasing 
Rainbows, To Love Again, Concerto For Two — 
The Things I Love — Full Moon and Empty 
Arms — A Song Of Joy — If You Are But A 
Dream — Mozart 40 — Our Love, Save Me A 
Dream, Moon Love, Starry Night — Tristesse 

— Strange Music — Stranger In Paradise, 
Baubles, Bangles and Beads, This Is My 
Beloved — My Reverie — Moonlight Madonna 

— My Heart Reminds Me. 

Full marks to Wilbur Kentwell, to Conn, to 
producer Ron Wills and to recordist David 
Woodley-Page. Recommended. (W.N.W.) 


THIS IS POURCEL. Franck Pourcel and 
his orchestra. Columbia stereo SOEX 
9867. 

Sampler albums are usually, in my 
opinion, not good buying. But this disc, 
featuring 14 tracks from Franck Pourcel’s 
albums, is one of the exceptions. Fora start, 
its price of $2.95 puts it ahead. Secondly, the 
tracks link together to form a cohesive 
whole. Quality is up to a good standard 
throughout. 

Some of the titles are: Dancing In The Sun 
— A Man Without Love — Love At First 
Sight — Abacachi — Summertime — 
Anitra’s Dance — This is My Song — 
Adelita — Aranjuez Mon Amour. (L.D.S.) 


94 


ELECTRONICS Australia, June, 1972 


















DGG “Festival of Hits” Series 


MARIACHI INTERNATIONAL. Ace of 
Clubs stereo SCLA 7037. 

Want some authentic Mexican folk music 
as background for dining or those quiet 
drinks on the patio at sunset? Then this is 
the album for you. Sound quality is good 
throughout and the price is right at $2.95. 

Thirteen tunes are presented: 
Guadalajara — Cielito Lindo — 
Cucurrucucu Paloma — El Colas — Cancion 
Mixteca — Las Mananitas — Jarabe 
Tapatio — La Negra — La Malaguena — La 
Raspa — Zacatecas — Las Golondrinas. 
(L.D.S.) 

★ ★ ★ 

THE CORDOVOX MAGIC OF VALEN¬ 
TINO. HMV Stereo SOELP-9789. 

It must be admitted that the title of this 
disc does not sound very promising. It has 
connotations of a second-rate accordionist 
murdering popular tunes. But this is 
completely, misleading. For a start, the 
instrument used is not an accordion — it has 
all the electronics of a 4-channel organ built 
into it. And Valentino is to the Cordovox 
(call it what you will) what Liberace is to 
the piano. He even dresses in the same 
flamboyant style. He was born in Ireland, is 
a Bachelor of Music and has toured many 
countries, including Australia. 

Some of the tracks are a little trite. After 
all, how many musicians would care to 
dress up “Chopsticks” in the way he has. 
But most tracks are thoroughly enjoyable. 
The sound quality is good throughout and 
the stereo spread is naturally spectacular. 
At the price of $2.95 it is a bargain. 

There are 13 tracks in all, some presented 
in the form of a medley. Some of the tunes 
presented are: The Desperados — Love Is 
Blue — Mexican Whistler — Chihuahua — 
Harry Lime Theme — A Man Without Love 
— Yellow Bird. (L.D.S.) 

★ ★ ★ 

REUBERT HAYES PLAYS THE CONN 
“RHAPSODY’’ ORGAN. St. Columba’s 
Presbyterian Church, Lane Cove, 
Sydney. Mono, Parker PR-003. 

Reubert Hayes has long been an integral 
part of the organ scene in the Sydney area. 
He featured during the heyday of the in¬ 
strument in theatres, stayed with them 
during their eclipse and is now identified 
with R.H. Elvy and the Conn. 

The organ featured here is the “Rhap- 
sodie”, an instrument somewhere near the 
middle of the range. The occasion was a 
recital for a relatively small church group, 


MOZART FESTIVAL OF HITS Various artiste 
and orchestras. DGG stereo 2538 120. 

CHOPIN FESTIVAL OF HITS Various artiste. 
The London Symphony Orchestra con¬ 
ducted by Claudio Abbado. DGG stereo 
2538 121. 

TCHAIKOWSKY FESTIVAL OF HITS Various 
artists and orchestras. DGG stereo 2538 
122 . 


These new releases in the DGG series of 
"hits” by famous composers maintain the 
high standard apparent in the first releases 
reviewed last month. Once again, the material 
has been very well selected, it is played only 
by top ranking artists and orchestras under 
famous conductors, and the sound quality is 
generally good. These discs must be regarded 
as excellent value at the price of $3.98. 

Here is what they contain: 

MOZART: Symphony No 40, first movement 
— Piano Concerto No 21 (“Elvira Madigan”), 
second movement — Serenade for Wind 
Instruments, last movement — Ave Verum 
Corpus — Marriage of Figaro, March from 
Third Act — Piano Concerto No 27, last 
movement— Eine Kleine Nachtmusik, second 
movement — Turkish March from Piano 
Sonata in A — Symphony No 34, last 
movement — Chorus with Glockenspiel, from 
"The Magic Flute”. 

CHOPIN: Military Polonaise— Nocturne in 
E flat— Waltz in C sharp minor — Mazurka in 
A minor — Black Key study — Study No 3 
(“Tristesse”) — Polonaise in A flat — Fan- 
tasie Impromptu — Waltz in D flat (“Minute”) 


which turned into a recording session only 
because a representative of Parker 
Records set up a single mic and tape 
recorder. 

What you hear, therefore, is a straight, 
unembellished performance, with no op¬ 
portunity for re-takes or fancy mixing. I 
only wish I could do as well in such cir¬ 
cumstances! 

The track titles: Sons Of The Brave — 
Excerpts: “Sound Of Music” — Jesu, Joy 
Of Man’s Desiring — Schubert; The Im¬ 
mortal — Intermezzo — Excerpts: “The 
Student Prince” — Evensong — 
Mediterranean Melody — La Paloma — 
Toreador Song — Come Back To Sorrento — 
Chiribiribin — Oh Marie — O Sole Mio — 
Funiculi, Funicula. 


— Piano Concerto No 1, last movement. 

TCHAIKOWSKY: Polonaise from “Eugene 
Onegin” — Waltz from Serenade for Strings — 
Marche Slav — Overture, March and Chinese 
Dance from "The Nutcracker” — Waltz from 
Symphony No 6 — Pizzicato from Symphony 
No 4— Waltz from Symphony No 5 — Waltz 
from "Eugene Onegin”. 

The Mozart pieces are all eminently 
pleasing, but I question the inclusion of 
sections from major works lasting 70 seconds 
and 45 seconds, even in a “bits and pieces” 
disc of this type. Against this, one can set the 
relatively generous playing time required by 
the inclusion of several long complete 
movements on both sides of the disc. 

The Chopin disc provides an excellent 
example of contrast in styles. On the one hand 
there is the heavily romanticised style of 
Tamas Vasary, replete with wide rubatos and 
drastic tempo changes; on the other hand 
there is the penetrating, clearcut style of the 
brilliant young German pianist Martha 
Argerich. There is also a very dull per¬ 
formance of the "Military” Polonaise by the 
usually much more interesting Shura 
Cherkasky. 

The Tchaikowsky disc is particularly 
generous in playing time, and although one 
could question the inclusion of some items 
against the omission of others (nothing from 
"Swan Lake” ! ! ! ) the playing throughout is 
very satisfactory. 

Currently available DGG recordings con¬ 
taining full performances of the works 
represented in these selections are listed in 
the cover notes in each instance. (H.A.T.) 


The quality is clean, a little bass-heavy 
perhaps but good, considering the spon¬ 
taneous conditions under which it was 
made. (From Parker Recordings, 9 Carmel 
Place, Winston Hills, 2153. Price $5 plus 50c 
pack and postage). (W.N.W.) 

★ ★ ★ 

CONTEMPORARY AUSTRALIAN SONGS 
by Bryan Kryger Conway, sung by Doug 
Owens. Stereo, Festival SFL-934484. 

The rising standards of local record 
productions are reflected in this album, 
commissioned by “The Australian” 
newspaper, produced with the assistance of 
the Australian Performing Rights Society, 
and manufactured by Festival Records, 
who presumably were also responsible for 



9 10 11 12 13 14 %, 5 

I J I » I » I « I I I * | 


17 17 8 

» . I I I 


■ 


_I 


RE-DISCOVER RADIO WITH THE AM100 MK11 TUNER 

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_35 HEATHER STREET, COLLAROY PLATEAU, NSW 2098. PHONE 982 1147 


ELECTRONICS Australia, June, 1972 95 









TRANSISTOR STEREO AMPLIFIERS WITH IN-BUILT AM TUNER 
ULTIMATE IN DESIGN — LONG DEPENDABILITY 

USING ALL SILICON TRANSISTORS 40 WATTS - RMS 


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From 20 to 20,000Hz±IdB. 
HARMONIC DISTORTION: 

Less than 1 per cent of rated output. 
HUM AND NOISE: 

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INPUT SENSITIVITY: 

Mag 3mV, Aux 200mV. 

SPEAKER IMPEDANCE: 8 ohms. 
EQUALISED: Mag RIAA. 

TONE CONTROLS: Bass, 50Hz + 12dB; 
Treble, 10KHz±12dB. 

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SCRATCH FILTER: 

(High filter) at lOKHz 9dB. 

RUMBLE FILTER: 

(Low filter) at 50Hz 5dB. 

PROVISION FOR TAPE RECOR¬ 
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plug connection. 

PROVISION FOR HEADPHONES: 

With headphone 7 speaker switch on 
front panel. 

DIMENSIONS: I 6 V 2 x 5V 2 x llin deep. 
TUNER : This unit can be supplied with 
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coverage of 530 to 1600 KHz. Calibrated 
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THE CIRCUIT incorporates regulated 
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A high quality stereo amplifier incorporating the new Plessey SL403D I.C. audio am¬ 
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available in teak or walnut oiled finish. 

SPECIFICATIONS: 

DISTORTION: 

Less than 1.5 per cent THD at lKHz, less than 0.5 per cent at lOOmWat lKHz. 

SIGNAL TO NOISE RATIO: 

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Within 2dB from 20Hz to 100KHZ. 

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INPUT SENSITIVITY: 

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SHORT CIRCUIT PROTECTION. 


Above amplifier tuner supplies with two Magnavox 8 WRMkV speakers, two 3TC tweeters, 2 4mfd. condensers and Garrard 
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Post and packing $1.50 


CLASSIC RADIO 

245 PARRAMATTA ROAD, HABERFIELD, 2045 N.S.W. PHONE 798 7145 


96 ELECTRONICS Australia, June, 1972 










the high-quality recording. The disc comes 
packaged in a lavishly produced folding 
sleeve adorned with paintings by John 
Darbyshire of old gold towns of Victoria. 

The music is country and western 
orientated, and could have come from the 
studios of Nashville — except towards the 
end of side 2, where something definitely 
of Australian character is discernible. 
However, there is no doubting the 
Australian character of the lyrics, which 
are mostly more interesting and have 
greater character-than the tunes. I think 
this can be discerned from the titles: ‘Til 
the Walls Came Tumbling Down — Yellow 
River Yarra — Wayback — Farewell — 
Riverine — Menindee Wind — I Look for a 
Valley — Seven Years Ago — Witchety 
Witchety — Native Companion — Inverell. 
My suggestion is — give this disc a try. Ask 
your retailer to let you hear a few tracks. I 
think you will like what you hear. Try 
“Witchety Witchety”, which with its did- 
jeridoo accompaniment and aboriginal 
terms should appeal to those becoming a 
little tired of the commercialised C & W 
material of Nashville. (H.A.T.) 

★ ★ ★ 
HOLIDAY IN ITALY. La Banda del 
Mandolino conducted by Norrie 
Paramor. Polydor stereo 2371 219. 

Some albums are certainly very well 
named and this is one of them. The music 
has an idyllic Neapolitan charm that 
quickly puts you in a carefree mood. In 
terms of sound quality, I found the man¬ 
dolins a trifle overbright but this is easily 
corrected by the tone controls. Surface 
noise on my pressing was low. Stereo 
spread was even and wide. 

There are twelve tracks in all: Chir- 
ibiribin — Come Back To Sorrento — The 
Magic Of Loving — Don’t Let Tonight Ever 
End — Everyday A Little Older — Catari 
catari — 0 Sole Mio — Help Yourself — A 
Man Without Love — Santa Lucia — Love 
Me Tonight — Arrividerci Roma. (L.D.S.) 
★ ★ ★ 

LOVE BOOK. The Lettermen. Capitol 
stereo ST 836. 

The Lettermen are a male vocal trio with 
rather ordinary voices but they have an 
ability to harmonise and to inject just the 
right amount of feeling into their songs. Any 
more and it would be maudlin. As such, the 
album forms just the right background for a 
romantic evening. 

The instrumental arrangements are very 
appropriate and the sound quality is good. If 
you like the Lettermen, you can buy without 
hesitation. 

Titles on the disc include: Love — Wed¬ 
ding Song — Theme from “Love Story” — 
How Can You Mend A Broken Heart — Aint 
No Sunshine — I’m Leavin’ — Don’t Pull 
Your Love. (L.D.S.) 

★ ★ ★ 

THE INCOMPARABLE EDITH PIAF. 
Stereo, RCA Camden CAS 2570. 

Since Edith Piaf’s career continued well 
into the LP period, and even into the stereo 
era, she must presumably have made 
records for LP and perhaps stereo masters. 
However, these tracks seem to be 
remastered from 78rpm discs, and some of 
them sound quite old, with poor quality 
sound and background noise. Despite this, 
the disc is certain to be eagerly sought by 
those who fell under Piaf’s spell, especially 
at-the Camden price of $2.75. 


She sings the following ten songs Amour 
du Mois de Mai — Une Chanson a Trois 
Temps — Si Tu Partais — Monsieur X — 
Les Cloches Son — Le Geste — Les Vieux 
Bateaux — Sophie — Cousu de Fil Blanc — 
Monsieur Ernest a Reussi. 

Do not be taken in by the other titles listed 
in the credits. This shows the first number 
as “La Vie en Rose”, a Piaf standard, and I 
feel a great many people will be disap¬ 
pointed to find, after buying the disc, that 
Edith Piaf does NOT sing it here. It is 
hummed by a background female choir, 
during an announcement in French before 
the artist comes on stage. Three other 
numbers are treated the same. (H.A.T.) 

Also received . . . 

The following records have not been played 
all through, but have been sampled to 
assess technical quality. Unless other¬ 
wise stated, the discs may be assumed to 
be technically satisfactory. 

IT’S A SIN TO TELL A LIE. Slim Whitman. 
Stereo, United Artists (Festival) SUAL- 
934363. 

Contents: It’s a Sin to Tell a Lie — Follow 
It — You, You, You — One For You — 
Sunshine — Near You — The Loveliest 
Night — Something Beautiful — That’s 
Enough For Me — It Takes a Lot of Ten¬ 
derness — Redwing — Tammy. 

KNOCK THREE TIMES AND MORE. The 
City of Westminster String Band. Stereo, 
Astor SPLP 1381. 

Contents: Never Ending Song of Love — 
It’s Too Late — What Are You Doing on 
Sunday — I’m Still Waiting — Say One Word 

— Me and You and a Dog Named Boo — 
You’ve Got a Friend — Knock Three Times 

— Oh You Pretty Thing — Are We To Blame 

— How Can You Mend a Broken Heart — Co 
Co 

THE WORLD’S MOST BEAUTIFUL LOVE 
THEMES. Bob Ralston, piano, with 
orchestra. Stereo, Calendar (Festival) 
SR66-9887. 

Contents: Theme from “Love Story” — 
Close to You — If I Loved You — A Time for 
Us — We Loved by Starlight — Don’t Take 
Your Love Fiom ME — I Was Born In Love 
With You — Love is Here to Stay — Ann 
Affair to Remember — Love Theme from 
“La Strade” — Story of Three Loves — Our 
Love. 

SIXTEEN GREAT PERFORMANCES. 
Tony Mottola. Stereo, Probe (EMI) SPSS 
9875. 

Contents include: Satisfaction — Vaya 
Con Dios — Brasilia — Skip to My Lou — 
Arriverderci Roma — Carnival Time — 
Yesterday — Am I Blue — Tenderly — 
Tijuana Taxi — Volare. 

WARM FEELINGS. Tony Mottola. Stereo, 
Project 3 (Festival) SPJL-934358. 

Contents: Make It With You —• Tea for 
Two — Theme from “Love Story” — 
Watchin’ Scotty Grow — For All We Know 

— It's Too Late — Time and Love — Star¬ 
dust — It’s Impossible — Rainy Days and 
Mondays — If — Warm Feelings. 

GUITAR ’72. Al Caiola. Stereo, Interfusion 
(Festival) SITFL-934292. 

Contents: It don’t Come Easy — If — Put 
Your Hand In Mine — Me & You & a Dog 


"INNERBOND" 

(Regd.) 

BONDED 

ACETATE 

FIBRES 

FOR PACKING IN 

SPEAKER ENCLOSURES 


A new resilient Bonded Wadding made 
from ultra fine Cellulose Acetate 
Fibres that gives high efficiency for 
sound absorption. 

"INNERBOND" is light, clean, dust- 
free and easy to handle. Because all the 
fibresare bonded "INNERBOND" will 
hang as a "curtain" and will not 
fracture or break down due to 
vibration. 

"INNERBOND" is odourless, highly 
resistant to attack by bacteria or 
fungus and is vermin repellant; 
"INNERBOND" at 16oz sq. yd. has a 
normal thickness of 1" and at this 
density is recommended as a packing 
in speaker enclosures for sound ab¬ 
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STOCKISTS: 

SYDNEY: Arrow Electronics Pty. Ltd. 342 Kent 
St.; Instrol HI-FI Pty. Ltd., 91a York St.; 
Convoy International Pty. Ltd., 449 Kent St.; 
Encel Electronics Pty. Ltd., 257 Clarence St.; 
Kent HI-FI 432 Kent St.; Mastersound Sales 
Pty. Ltd., 400 Kent St.; Radio Despatch Ser 
vice, 869 George St.; Peter Shalley Electronics 
Pty. Ltd., 127 York St., Stereo Music Systems, 
193 Clarence St.; Circuit Components (A / sia) 
Pty. Ltd., 460 Bexley Rd., BEXLEY; Classic 
Radio, 245 Parramatta Rd., HABERFIELD; 
Dyna Stereo Pty. Ltd., 331 Prince's H'way, ST. 
PETERS: Albert Wright Radio Service, 795 
New Canterbury Road, HURLSTONE PARK: 
H. B. Radio Products, 103-105 Catherine St., 
LEICHHARDT; Semicon Electronics, 172 
Carlingford Rd., EPPING. 

CANBERRA: Kitchen and Hi-Fi Specialists, Cnr. 
Giles and Kennedy Sts., Kingston. 

NEWCASTLE: Martin de Launay Pty. Ltd., King 
and Darby Streets; Dynamic Sound, 587 
Hunter Street. 

WOLLONGONG: Dapto TV Service, 156 Prince's 
Hwy., Dapto. 

MELBOURNE: J. H. Magrath and Co. Pty. Ltd., 
208 Little Lonsdale Street. 

BRISBANE: Chandlers Pty. Ltd., cnr. Albert and 
Charlotte Streets; Brisbane Agencies, 78 
Wickham Street, Fortitude Valley, Stereo 
Supplies, 100 Turbot St. 

IPSWICH: Robert N. Smallwood, 205 Brisbane 
Road, Booval. 

NORTH QUEENSLAND: Alvin Communications 
and Electronics, 38 Pegnall St., Pimilco, 
Townsville. 

ADELAIDE: Duncan Agencies, 57 Woodville 
Road, Woodville; General Accessories, 81 
Flinders Street; Trustcott Electronics, 62-64 
Hindmarsh Square. 

PERTH: Atkins (W.A.) Ltd., 894 Hay Street; 
Carlyle and Co. Pty. Ltd., 1 Milligan Street; 
General Accessories, 46 Milligan Street. 

HOBART: Homecrafts-Tasmania, 199 Collins 
Street. 


If unobtainable 

For 1 sq. yd. as above send $2.00 
For 2 sq. yds. as above send $3.75 
For 4 sq. yds. as above send $6.50 

Postage paid in Australia and Territories 
to the manufacturers. 

WONDER WOOL 

PTY. LTD. 

87 JAMES STREET, LEICHHARDT, 
NSW 2040. 

Box 548 — GPO, Sydney 2001. 
Phone: 56 2780. 


Australia, June, 1972 97 










THE NEW ADC-XLM 

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Interstate Distributors: — 

NSW: Electronic Parts Pty Ltd, 91a York St, Sydney. 

SA: The Muses Pty Ltd (Sound Spectrum), 33 Regent Arcade, Adelaide. 
Old: Brisbane Agencies, 72 Wickham St, Valley, Brisbane. 

WA: Arena Distributors (Australia) Pty Ltd, 196 Adelaide Tee, Perth. 
Victoria, Tasmania & NT: J. H. Reproducers Co. 


National Distributors: 

J. H. REPRODUCERS CO, 

293 HUNTINGDALE RD, CHADSTONE, VIC. 3148. 
TELEPHONES: 277-3066, 277-3488. 



98 ELECTRONICS Australia, June, 1972 













Named Boo — Bermuda Sand — Jesus 
Christ Superstar — I Didn’t Know How To 
Love Him — Another Day — Watchin’ 
Scotty Grow — Theme from “Love Story”. 

Jazz and Rock.... 

MORNING OF THE EARTH. Film sound¬ 
track. Warner Brothers stereo WS 20004. 

The Australian surf was the inspiration 
for the songs on this album, which is an 
outstanding contribution to the modern rock 
scene. The film is unnecessary to en¬ 
joyment of the recording. 

This stands as a great collection of songs 
by young writer's. G. Wayne Thomas opens 
the album with “Morning of the Earth” a 
delicate song linking the sea with creation. 
There are a number of his songs on the 
record — “Open Up Your Heart” and “Day 
Comes” are outstanding. 

Brian Cadd captures the mystery of wave 
motion in “Making It On Your Own” and 
“Come With Me”. He is an outstanding 
Melbourne writer and performer. 

The LP was recorded at TCS, Melbourne 
by engineer John French. The sound is 
good. Taman Shud sound suitably heavy 
with “First Things First”, “Bali Waters” 
and “Sea the Swells”. This is one of the few 
rock records you’ll hear with an Australian 
sound. (G.W.) 

★ ★ ★ 

FLAMING GALAH. Fraternity. RCA stereo 

SL 102038. 

With a strangely discordant opening, this 
LP moves into a performance of out¬ 
standing character. The members formerly 
belonged to the hard rock outfit, Levi Smith 
Clefs. In February of last year they left the 
big smoke and moved into a rural property 
in the Adelaide hills. 

They had developed a number of originals 
which fit into the country rock scene. Ap¬ 
plying the musical language of American 
folk rock to an Australian environment 
can’t be expected to produce permutations 
overnight. 

We can detect some of the elements of 
antipodean culture in songs like “Welfare 
Boogie”, “If You Got It” and “Hemming’s 
Farm”; elements such as repetition, a 
move toward surrealism and a gradual 
emergence of the solitary voice. 

The danger of rustic returns is that the 
creative artisit may go under before the 
weight of English music hall tradition which 
is still the dominant musical influence in the 
bush. Fraternity’s performance on this LP 
shows that they have retained their ob¬ 
jectivity. 

John Robinson’s “Seasons of Change” is 
the keynote tune of the album. Numbers 
written by the group are better than this. 
John Eyers, Bruce Howe, Bon Scott, John 
Freeman, Mick Jurd, John Bisset and Sam 
See are Fraternity. The LP was recorded by 
Bill Armstrong in Melbourne with engineer 
John Sayers. (G.W.) 

★ ★ ★ 
FRESH WATER. Alison McCallum. RCA 

stereo SL 102 036. 

A high powered blues performance comes 
from a young lady who has been referred to 
as Australia’s Janis Joplin. 

The production of the album, by Simon 
Napier Bell, is exceptional. “Superman” 
comes out particularly well. This is a theme 
which fascinates Australian composers. 
There are a number of tunes around using 
this idea and all of them &re outstanding. 


“Ain’t Eatin’ Dinner Tonight” has the 
abrasive edge of a jazz performance about 
it. Alison bites out the lyrics in an exciting 
performance. The backing musicians, not 
named, sound like some of Australia’s best 
hot players. 

She takes “Any Way You Want Me” at a 
more thoughtful pace, building up to a 
crescendo in the closing choruses. 

I don’t like the device of fading the ride¬ 
out endings of some of the tracks. It’s a 
throwback to the days of the 78s when the 
performance had to end though the band 
played on. (G.W.) 

★ ★ ★ 

CHILDHOOD’S END. Phil Sawyer. Sweet 

Peach stereo SPB 505. 

As an example of Adelaide cool, this 
album will take some beating. It features 
the original compositions of Phil Sawyer 
sung against some excellent backings 
arranged by Phil Cuneen. Earlier Sweet 
Peach albums have been noted for the 
professionalism of the backings and this 
one is also in world class. 

Sawyer has appeared on a number of LPs 
from Adelaide. His songs are sensitive and 
imaginative. “Childhood’s End” “Electric 
Children” and “The Chase” are interesting 
poems set to music. “Where Did Everybody 
Go?” is an ironic piece, part political, in the 
Bob Dylan tradition. 

Stan Lewandowski was responsible for 
engineering on “Electric Children”. I won’t 
try to guess how the sounds were produced. 
(G.W.) 

★ ★ ★ 

HISTORICAL FIGURES AND ANCIENT 

HEADS. Canned Heat. United Artisits 

stereo SUAL 934483. 

This rock group is one of the best 
American contemporary outfits playing the 
blues. For this session they invited a 
number of guests. The most outstanding 
was Little Richard who performs 
outrageously on “Rocking with the King”, 
King Richard, of course. Richard joins Bob 
Hite for the vocal. 

Flute player Charles Lloyd plays on “I 
Don’t Care What You Tell Me” and Harvey 
Mandel is guest guitarist for “That’s All 
Right”. 

The blues of Canned Heat are happy and 
extroverted, enjoyable to listen to, 
professionally played with musical values 
as the first consideration. (G.W.) 

★ ★ ★ 

EXCLUSIVELY FOR MY FRIENDS. 

Oscar Peterson. MPS stereo 15 181. 

This intriguing album was recorded in 
Villingen, Germany in the private recording 
studio of Hans Georg Brunner-Schwer. It is 
no ordinary studio. 

Brunner-Schwer was formerly co-owner 
of Saba and is now the owner of MPS which 
took over Saba. The fidelity of the sound is 
astonishing. Peterson, who plays so well 
with a rhythm section, is a superb soloist. 

The album opens with a performance of 
Gershwin’s “Someone to Watch Over Me”, 
played as a tribute to the descending runs 
and fantasies of Art Tatum, a pianist to 
whom Peterson acknowledges a tremen¬ 
dous debt. “I Should Care” on the other 
hand, displays many of the devices which 
are particularly Peterson. 

The concert is one of jazz standards, 
delightful examples of form which are the 
natural materials of jazz. (G.W.) ® 


CORRECTION! 
SONY PRICES 


Since we prepared aur two-page ad¬ 
vertisement "Presenting the Sony All Stars" in 
the April issue of Electronics Australia, Sony 
suggested retail prices, like prices of quality 
equipment all over the world, have necessarily 
risen. 

The correct suggested retail prices for the 
items listed now are: 

TC-440 (Stereo tape recorder) $525 

TC-366-4 (quadradial deck) $727 

TA-1130 (amplifier) $573 

TA-1140 (amplifier) $375 

TA-2244 $388 

PS-5520 (turntable) $221 

TC-160 (cassette tape deck) $281 

SS-7600 (speakers) $399 each 

SS-7300 (speakers) $208 each 

SS-4200 (speakers) $139 each 

SS-4300 (speakers) $169 each 

We sincerely regret any inconvenience this 
may have caused. 

JACOBY KEMPTHORNE 
Australian distributors. 

SYDNEY: 26 2651, MELBOURNE: 329 6866, 
ADELAIDE: 93 2388 / 9, PERTH: 28 5725, 
BRISBANE:44 4488, LAUNCESTON: 2 5322. 
Agents: CANBERRA: 47 9010, NEW¬ 
CASTLE: 61 4991, FAIRY MEADOW: 
84 8022. 

For further information on any of these Sony 
models, please fill in the Reader Information 
Service coupon in this issue. 


LAFAYETTE of u.s.a. 

1972 CATALOGUE 720 


GUIDE TO 

EVERYTHING 

IN 

ELECTRONICS 
468 pages 


• AMATEUR RADIO • 27MHz 2-WAY 
RADIO 

• TEST EQUIPMENT • COMPONENTS 

• HI FI STEREO AMPLIFIERS, SPEAKERS, 
ETC. 

THOUSANDS OF INTERESTING ITEMS are 
detailed in the 1972 catalogue of Lafayette Radio 
Electronics Corporation of U.S.A. All are 
available, some from Australian stocks — list 
included — others for shipment from the U.S.A. 
Many exclusive LAFAYETTE lines are featured. 
Mail coupon below or write. 



LAFAYETTE ELECTRONICS, 

div. of Electron Tube Distributors Pty. Ltd., 94 
HIGH ST., ST. KILDA, VIC., 3182. 

Please send me Catalogue 720. I enclose 
Chq. / P.O. for $2.50 which is refundable with my 
first order for $25. 


NAME. 


ADDRESS. 


P./ Code. a 

--_-- - - - — — J 


ELECTRONICS Australia, June, 1972 99 











PRODUCT REVIEWS 
AND RELEASES 


Cassette deck has glass crystal ferrite heads 



The Akai GXC-40D was submitted by Akai Australia Pty Ltd. Notable 
features are; a glass-crystal ferrite head, an overload protection circuit and 
the means to increase AC bias amplitude for chromium dioxide tapes. 


The Akai GXC-40D has an attractive 
appearance. Overall dimensions are 16(w )x 
4-7 8(h) x 8-5 8(d) inches (412 x 122 x 222 
mm) including knobs and feet. The cabinet 
is teak veneered plywood, while the base 
and panel are formed from moulded plastic. 

Three pushbutton switches are used for 
power, pause and eject. Two slide pots 
calibrated 0 to 10 allow recording levels to 
be set separately for each channel with the 
aid of two level meters calibrated -20VU to 
+6VU. In our opinion, these meters are 
rather difficult to read unless viewed 
closely. 



For locating defective electrical 
parts, faulty electronic connect¬ 
ions, protecting parts when 
soldering. 


FOR ELECTRICAL, INDUSTRIAL, ELECTRONIC, MEDICAL 
USE-non-toxic, non-inflammable, FREEZES INSTANTLY! 


Available from your accredited CRC Distributor 


A toggle switch situated directly above 
the eject button switches in an overload 
protection circuit. We tested this circuit by 
recording a 1kHz sinewave while increasing 
the input; the maximum VU reading was 
4-3 and no clipping was apparent on 
playback, although the input was increased 
to 10 volts. It may be noted that the input 
sensitivity for zero VU was 48mV, which 
gave an output off normal tape of 1.1 volts. 

Situated to the right of the overload 
switch is a bias switch which increases the 
record bias and erase current when 
chromium dioxide tape is being used. 
Behind the cassette well is a resettable 3 
digit counter, which we found was fairly 
accurate; cueing was no problem. A two 
step tape release mechanism allows the unit 
to be operated while the tape well lid is 
open. The cassette will eject during all 
modes except record and play. 

Functional facilities also available at the 
front of the panel include a stereo phone 
jack and microphone jack for each channel, 
while at the back of the unit we find (left to 
right) a screw-in fuse holder cum voltage 
selector, four phono sockets (two input and 
two output) and a 5-pin DIN socket which 
takes care of input and output for both 
channels. Also supplied is a 3ft connector 
cable with a five pin DIN plug on one end 
and four phono plugs on the other. 

The tape transport operates very 
smoothly and can only be heard on rewind 
and fast forward modes. Mode switching is 


interlocked, in fact one may switch modes 
(not including record) at any desired rate 
without any problem. 

A feature mentioned earlier is the glass 
crystal ferrite head. This head has a 
crystal ferrite core instead of the usual 
permalloy type and the whole assembly is 
encased in glass before the shield is added. 
This construction is claimed to increase 
service life, improve sensitivity due to a 
shallower gap and eliminate the build up of 
dust and residue in the gap. 

The first test we ran with this unit was 
frequency response. Akai do not quote a 
reference input level for their test so we 
assumed the usual level of -20VU. For this 
test the record level control was maintained 
at maximum while recording. We ran this 
test with both normal and chromium 
dioxide tape , in each case we were able to 
verify Akai s results. 

Akai quote, and we verified for normal 
tape, response from 30Hz to 16kHz (+3dB), 
and on chromium dioxide tape from 30Hz 
to 18kHz ( + 3dB). We found with both types 
of tape, that response from 25Hz to 8kHz 
was relatively flat while between 9kHz and 
15kHz a small peak occurred. 

The signal to noise ratio varied for each 
type of tape. With normal tape we measured 
43 dB while the figure for chromium dioxide 
tape surprisingly deteriorated to 36dB, 
which would indicate that either the record 
bias amplitude on this particular unit was 
not set to the optimum level for chromium 
dioxide tape or the unit was faulty. Akai 
quote S to N as better than 45dB, but give no 
reference to tape used or recording level. 
Our reference recording level for this test 
was zero VU. 

No figures were given for crosstalk. We 
measured crosstalk at 100Hz, 1kHz and 
10kHz with reference zero VU recording 
input; the results for normal tape were 
-31dB, -32dB and -23dB (as frequency in¬ 
creases). With chromium dioxide tape the 
results improved to -36dB, -32dB, and -27dB. 
Total distortion measured (1kHz OVU) was 
2 % with normal tape and 3% with 
chromium, again highlighting that bias 
problem. Akai state less than 2 % with no 
reference to tape used. 

We recorded some familiar discs on 
normal tape and compared the results 
audibly. Our impression was that the 
recorded music had slightly accentuated 
highs and slightly more obvious hiss. When 
we applied the same comparison to music 
recorded on chromium dioxide tape the 
overall frequency response appeared to 
remain flat but the hiss was still obvious, as 
one would expect from the test results. 

Overall the GXC-40D performs well and 
meets the majority of the manufactuers 
specifications. The unit performs well with 
normal tape but with the present unit it 
would not really be fair at this time (due to 
the problems mentioned) to comment on 
performance with chromium tape. The 
suggested retail price of $279 places this 
unit in a price range where machines 
having Dolby systems are available. 

The Akai GXC-40D is now available in 
Australia from selected retailers and is 
distributed by Akai Australia Pty Ltd, 276 
Castlereagh Street, Sydney, NSW, 2000. 
(G.N.). 


100 


ELECTRONICS Australia, June, 1972 







Neat & compact power supply 


New lab-type power supply is neat, compact and fully stabilised. Ten turn 
voltage and current controls allow precision adjustment over ranges 0 to 25 
volts and 0 to 1 amp. 


The Scientific Electronics 512A supply 
comes in a compact case finished in satin 
black, while the front panel which is a 
continuation of the base is silver anodised. 
Overall dimensions are 6Vs (w) x 9% (d) x 
4V 2 (h) inches, or 146 x 238 x 115mm. The 
unit has minimum controls, namely two ten 
turn pots for voltage and current levels, 
together with a slide switch which allows 
one to monitor either voltage or current 
using the single panel meter. However these 
appear to be quite ample. 

Three output terminals are provided, 
namely positive, negative and ground. The 
positive and negative terminals are fully 
floating, thus any voltage source up to 300 
volts can be connected between ground and 
the positive or negative terminals. 

The meter has a face measuring 2V 2 x 1V 2 
inches. The voltage range is calibrated 
from 0 to 25 volts in 5 volt steps, with fine 
scale markings every volt. The current 
range is calibrated from 0 to 1 amp in 0.2 



amp steps, with fine scale markings every 
50 mA. We found the meter calibration at all 
levels to well within normal limits. 

Scientific Electronics quote constant 
voltage regulation for full load as less than 
.005 % This was effectively verified as we 
could not detect any significant voltage 
variation from zero to maximum load 
current, using our Solartron LM1619 digital 
voltmeter. Line regulation is good; we could 
not detect significant variation in current 
or voltage levels for mains variations of 
±10% (the quoted figure is less than 0.01%). 
Ripple in the constant voltage mode was 
under lmV, less than quoted; in the con¬ 
stant current mode we found it un- 
measurably low. 

The supply is designed to change from 
constant voltage to constant current mode 
in the event of a current overload or output 
short circuit. When the output voltage / load 
resistance ratio exceeds the current level 
setting, the unit thus becomes a constant 
current source. Quoted load regulation in 
this mode is less than 0.02% current varia¬ 
tion for maximum full load voltage varia¬ 
tion. The limit of reading of our instruments 
again prevented us from verifying this, but 
the figure was certainly less than 0.5%. 

One aspect which we would criticise is the 
fact that the top of the control panel does not 
appear to be sufficiently secured; it tends to 
move slightly when one adjusts the controls. 
Apart from this the 512A is a sound unit and 
meets all of the specifications given. 

Price of the supply can be obtained on 
application to Scientific Electronics, 42 
Barry Street, Bayswater, Victoria, 3153, or 
selected dealers. (G.N.). 


DC-DC converter operates from car lighter socket 


New on the battery eliminator scene is a DC- 
DC car converter from A & R Electronic 
Equipment Pty Ltd, intended as a secondary 
supply source for cassette recorders, trans¬ 
istor radios and the like. It should fill a need 
for those who require a quick and easy way of 
reducing battery costs when operating such 
equipment in a motor vehicle. 

The converter consists of a simple transistor / zener 
regulator circuit housed in a cylindrical plastic body. 
The end of the body forms the necessary plug for in¬ 
sertion in a conventional auto cigar lighter outlet. Two 
output voltage levels are selectable by a small slide 
switch, 6or 9 volts from a 12 volt input. 

The regulator is assembled with the selector switch 
on a small printed board which fits neatly inside the 
large section of the converter body. A length of 
miniature “figure 8“ flex about lVfeyds (1.3m) long 
carries the output of the converter to a small coaxial 
connector having its outer sleeve positive. 

Although the converter is supplied as a 12 volt 
negative ground unit with the output connector sleeve 
as positive, there is no difficulty ift opening the unit to 



make changes to either the input and/or output, 
polarities as required. 

Specifications: Input: 12V DC. Negative chassis 
system. Output: 6 or 9 volts DC at 300mA maximum. 
Suggested retail price: $5.99; Trade: $3.45, plus 27Vfe% 
sales tax. Available from A & R Soanar Group 30-32 
Lexton Road, Box Hill, Victoria 3128, or any of their 
distributors. (G.F.H). 



—an all-transistor 2-track hi-fi tape 
recorder offering a maximum of fea¬ 
tures for its price. The Beocord I 100 
has 3 tape speeds: 4.75 cm/sec. ( I ^in/ 
sec.), speech recordings; 9.5 cm/sec. 

(3^in/sec.), recordings of gramophone 
and AM radio programmes: 19 cm/ 
sec.) Tjin/sec.), for exacting record¬ 
ings of FM radio programmes and 
direct microphone recordings of music. 
All reel sizes up to 18 cm (7in.). 
Output amplifier delivering 10 watts 
of audio output. Automatic recording 
level control which may be switched 
on and off as desired. Two smooth¬ 
running slack absorbers take up slack 
so as to ensure smooth starting and 
'stopping at all speeds. Electronic 
overload protection. Variable monitor¬ 
ing of the recorded signal. Top-quality 
tape transport mechanism with Pabst 
motor. 

Smooth-operating tape control lever. 
Large pointer instrument, for visual 
recording-level monitoring. Input 
selector for gramophone, radio, and 
microphone. Separate bass and treble 
controls. Pause control lever with 
editing position. Automatic stop at 
end of tape. Tape counter. Speed 
selector with on/off switch. Sockets for 
extension speaker and low-impedance 
microphone. All socket connections 
follow international DIN standards. 
Built-in tape splicing groove. 

Permits recording from one tape 
recorder to another. Pilot lamp shows 
light when power is applied. May be 
used as a separate microphone, radio, 
qramophone, or guitar amplifier. 

The Beocord I 100 is elegantly 
designed as an easily portable cassette 
model with carrying handle and 
built-in loudspeaker. Absolutely the 
best choice of tape recorder in this 
price range. 

DIMENSIONS: 202 mm high, 455 mm 
wide, 295 mm deep (8 x 17 15/16 x 
II 5/8 in.). Choice of teak, rosewood, 
or oak. 

THE BEOCORD 1100 is the ideal 
machine for background music in 
shops, cafes and factories and can 
also be used for domestic recording 
after hours. This machine also provides 
an invaluable aid to schools in drama 
and music departments. Please ring 
for a demonstration at . . . 



HI-FI 


698 Burke Rd., Camberwell 
82-4839 
Shop 9 

Southern Cross Hotel 
63-8930 


ELECTRONICS Australia, June, 1972 


101 















NEW SONY TAPE RECORDER 




TC-440 has rotating 
heads, auto reverse 


A rotating head block for bidirectional recording, dual capstan closed-loop 
tape drive and auto reverse are some of the features which enhance the 
Sony TC-440. This unit was submitted for review by Jacoby Kempthorne. 


The Sony TC-440 is an eye catcher. 
White borders surround all control 
notations, giving a projective appearance. 
Overall dimensions are as follows: 16 (w) x 
15 3 /4 (d) x 8 (h) inches including feet and 
knobs. 

Facilities include two miniature 
microphone jacks, a stereo phone jack, and 
a potentiometer for sound on sound and 
echo level controls, used in conjunction with 
a sound on sound-off-echo function slide 
switch. There is a tape select switch, which 
allows a choice of record and erase bias for 
either normal or low noise tape. 

There are individual VU meters for the 
left and right channels. These meters are 
easy to read, they are well illuminated and 
calibration (-20 to +3 VU) is accurate. 

Three tape speeds are provided, namely 


7Vfe, 33/4 and V/s ips. There is a four digit 
resetable counter which we found relatively 
accurate. The motor in this unit is a 
hysteresis synchronous type. 

Of the three features mentioned in the 
introduction, many readers will be familiar 
with auto reverse techniques and dual 
capstans, but the roto-bilateral head 
assembly incorporated in this unit is 
original. Briefly this assembly has two 
heads mounted side by side in a block which 
is mounted on a horizontal shaft rotating in 
a bearing. The shaft is hollow and carries 
the leads to the heads. The assembly rotates 
180° mechanically via a cog attached to the 
end of the hollow shaft when the play key is 
pressed. Should the tape play right through, 
the auto reverse mechanism acts (if the 
tape has a metal leader) and the head 




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COMMUNICATIONS 
RECEIVER 

SUGGESTED RETAIL PRICE F0R/F0A SYDNEY $191.00 

• 4 BANDS COVERING 540 Kcs. TO 30 
Mcs. 

• TWO MECHANICAL FILTERS ENSURE 
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• PRODUCT DETECTOR FOR S.S.fl. 'RE¬ 
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• AUTOMATIC NOISE LIMITER. 

• LARGE TUNING AND BANDSPREAD 
DIALS FOR ACCURATE TUNING. 

• CALIBRATED ELECTRICAL BANDSPREAD. 

• "S” METER AND B.F.0. 

• 2 MICROVOLTS SENSITIVITY FOR 10 
dB SI N RATIO. 


fA unit of Jacoby Mitchell Holdings Ltd) 

376 EASTERN VALLEY WAY, ROSEVILLE,2069. 
Cables and Telegraphic Address.- 'WESTELEC: 
Sydney. Phone 40 1212 
Please forward free illustrated literature 

and specifications on Trio equipment. 


Address 


102 



assembly is released to rotate back to the 
original position. 

Fast forward and rewind time for 1200 
feet of tape was 100 seconds. This unit has 
an end of tape auto stop mechanism and will 
not operate without tape. Sony quote 
frequency response with normal tape at 7Vfe 
ips from 30Hz to 20kHz (—3dB) and our 
figures verified this; however the quoted 
response at 3 3 / 4 and 1-7 / 8 ips of 20 to 17kHz 
and 30 to 9kHz respectively could only be 
obtained if the amplitude limits were ex¬ 
tended to ±4dB in each case. Our reference 
input for these tests was-20VU. 

Our figure for signal to noise ratio with 
normal tape at 7V 2 ips was 53dB which is 
exactly what Sony state. We measured 
crosstalk at 100Hz, 1kHz and 10kHz with 
normal tape at 7 ¥2 ips and reference input 
zero VU with the following results: (as 
frequency increases) -40dB, -41dB and 
-37dB. Finally we measured distortion at 
each speed off normal tape (1kHz zero VU) 
and obtained the following figures: at 7V 2 
ips 1.5%, at 3 3 /4 ips 1.5%and at 1-7/8 ips 2%. 

Before concluding we recorded some 
music tracks and compared the playback 
with that off disc. At 7V 2 ips there was no 
discemable difference. At 3 3 /4' ips the 
response remained flat but hiss was just 
noticeable, while there were less highs and 
slightly more hiss at 1-7/8 ips. 

In short, our tests show that the Sony TC 
-440 does do what the manufacturer 
claims. It is an attractive unit and should 
have considerable appeal for those seeking 
a high quality auto-reversing reel-to-reel 
machine. For $525 (suggested retail price) 
one gets the deck, two five foot leads with 
phono plugs on each end, a manual, auto 
reverse sensing foil and three head 
cleaners. 

The TC-440 is available from selected 
dealers and is distributed by Jacoby Kemp¬ 
thorne, 469-475 Kent Street, Sydney, NSW 
2000. (G-N.). 

★ ★ ★ 

New hybrid 1C amps 

STANDARD TELEPHONES AND 
CABLES PTY LTD, Moorebank Ave, 
Liverpool, NSW 2170, has a new range of 
low-cost hybrid IC audio amplifiers, with 
outputs ranging from 3W to 25W, and 
suitable for 8 ohm or 4 ohm loudspeaker 
loads. STC has also designed preamplifiers 
and power supplies for use with these 
amplifiers. Data sheets are available on 
application. 'See also the PA amplifier 
project elsewhere in this issue.) 


ELECTRONICS Australia, June, 1972 





















COMPACT RADIO TELEPHONE 



A new executive radiotelephone which combines efficiency with elegance 
has been introduced by Weston Electronics Pty Ltd. It exceeds all PMG 
requirements for 30kHz channelling. 

The Weston 551 VHF FM radiotelephone 


is a compact, attractively designed unit in a 
stylish lightweight vinyl-clad cabinet. It is 
an FM transceiver designed for installation 
in motor vehicles or other mobile situations, 
and operates on fixed crystal-controlled 
channels in the 70 : 85MHz, 92-94MHz, or 148- 
174MHz bands. Used with a 240V regulated 
power supply, it may also act as a base 
station. 

The equipment is all solid state, and in¬ 
corporates ICs and a protected dual gate 
MOSFET receiver front end. TTie trans¬ 
mitter is capable of sustained operation at 
25W full output, and the devices used are 
protected against antenna shorts or open 
circuits. Separate oscillators are used for 
each receive channel, and both transmitter 
and receiver oscillators are trimmer - 
adjustable for frequency netting purposes. 
Electronic switching is featured for remote 
channel selection. 

All power input circuits are floating, and 
either side may be externally earthed if 
desired. The set is completely guarded 
against accidental reverse polarity con¬ 
nections. An internal regulated power 
supply is provided for critical circuits. 


Construction is completely modular with 
plug-in printed boards being used for both 
RF and DC circuitry. This building-block 
construction simplifies the provision of 
remote operation or the adaption of the 
equipment for specialised requirements 
such as dual receivers and 20-channel 
operation. Options available include 
selective call, mute controlled operation of 
external equipment, remote operation, and 
talk-though repeater capability. 

Full technical details are available from 
Weston Electronics Pty Ltd, 376 Eastern 
Valley Way, Roseville, NSW 2069. 


GE METAL OXIDE VARISTORS 

A range of metal oxide varistors (MOVs) to eliminate or reduce voltage 
transients is now available through Australian General Electric Pty Ltd. 


Developed in the USA by General Electric Co, these 
devices are voltage dependent, symmetrical resistors 
which perform in a manner similar to back-to-back 
zener diodes in circuit protective functions, and offer 
advantages in performance and economics. 

The varistor impedance at voltages below normal is 
very high, but when exposed to high energy voltage 
transients, the impedance changes to a very low 
conducting value. The dangerous energy of the high 
voltage pulse is absorbed by the varistor, thus protect¬ 
ing any voltage sensitive circuit components. 

The instantaneous current through a varistor is 
proportional to the voltage across it raised to the power 
alpha. A GE-MOV has an alpha up to 70 with a 
guaranteed minimum of 25. By comparison, a resistor 
has an alpha of 1; selenium varistors from 5 to 15; and 
a power zener diode about 35. The higher the value of 
alpha, the sharper the transient suppression and the 
lower the clamping ratio. 



Initially, three type VP metal oxide varistors are 
available in Australia. All devices in the series are 
rated to a maximum operating temperature of 85°C 
with the maximum energy derated 3.8%/°C above 
that temperature. All have a maximum voltage 
temperature coefficient of —.05%/ °C. 

The currently available types are VP250A20, 
VP250A40 and VP420B40. They have the following 
maximum ratings: RMS input voltage 250V, 250V and 
400V respectively; Recurrent peak voltage 354V, 354V 
and 595V; Energy 20J, 40J and 40J; Average power 
dissipation 0.6W, 0.9W and 0.9W; Peak current for 
pulses less than 7us wide lkA, 1.25kAand 1.25kA. 

The main advantage of using GE-MOV varistors is 
low cost. The initial cost of a typical unit is low, but in 
addition with proper transient protection semiconduc¬ 
tors with lower ratings can be used in the associated 
circuit, for a further saving of cdst. 


Further details of the type VP metal oxide varistors, 
including price, may be obtained from Australian 
General Electric Pty Ltd, 86-90 Bay Street, Ultimo, 
NSW 2007. 


IRH Wirewound Pots 

Anew range of compact low cost 3W 
wirewound potentiometers is now 
available from IRH Components. 

The series AW is physically compatible with the CTS 
series 45, 15/ 16in diameter, commercial carbon pots, 
and can be combined to make any combination of 
straight or concentric tandem constructions with or 
without a switch. 

The new series features: high grade resistance 
element materials for long life reliability; glass filled 
nylon dust seal; gold plated collector ring for low 
noise; chemically sealed base material for very high 
insulation resistance; double contact wiper arm for 
reliable operation; one piece bush and plate. 



The AW series pots are available with resistances 

(Continued on Page 105) 


JUNE 

SPEAKER 

SPECIALS 


MAGNAVOX 8.30. 30 watts 
complete $58.00 

Cabinet Kit and Speakers $45.50 

MAGNAVOX 10WR and 3TC 
complete $48.50 

Cabinet Kit and Speakers $37.00 

MAGNAVOX 12WR and 3TC 
complete $50.50 

Cabinet Kit and Speakers $38.50 

WHARFEDALE SUPER 10 in R3 
Cabinet $80.00 

Cabinet Kit and Speakers $69.50 

WHARFEDALE Super Linton $56.50 
Cabinet Kit and Parts $45.00 


(Player Platforms $8.50. Tinted covers $8.30). 
Packing $1.25 per cabinet or kit. Freight on 
delivery. 

Send for Stereo Catalogue which includes 
Equipment Cabinets — Player Guide and Am¬ 
plifier Specials. 


H. B. RADIO SALES 

Makers of Radio and Radio Furniture for 
40 Years. 


105 CATHERINE STREET, 
LEICHHARDT, SYDNEY. 
Telephone :56 5580. 


TRANSISTOR SERVICE 

All Japanese and local 
sets repaired 


Aristone 

including ... 

Aurora 

Belair 

Berlin 

Crown 

Fujiya 

General 

Hitachi 

Kenco 

Mariner 

Mitsubishi 

Nanaola 

National 

Nivico 

Sanyo 

Sony 

Spica 

Standard 

Sharp 

Toshiba 

Yashica 


We do not sell spare parts 


PETER G. BOUGHTON 
99 Sussex Street, 

(near King St) 
SYDNEY, NSW 2000 
_Phone: 29 3845 


"OXFORD" 

RADIO CHASSIS - 

INSTRUMENT CASE- 
ENGRAVED & PRINTED PANEL 

"MINI BOXES” 
(Aluminium) 
HEATING SYSTEMS 
PTY LTD 

19-21 The Boulevarde, 
Caringbah 2229 
Phone 525-5222 
4 lines 


ELECTRONICS Australia, June, 1972 


103 


















The World’s Most 


Versatile Circait Binding System! 



INSTRUCTIONS 

R*movt paper backing and place 
adh«»ive tide downwards in Che 
s«rl*u«-d position. Press down firmly. 
When used with plain board drill 
from the *Cir«K»t’ side. Pass through 
component lead, bend over and cut 
to length. Solder in usual way. 
When used with ‘punched* board 
lay strip between rows of holes, 
pass component leads through holes 
adjacent to strip, bend the leads 
over the strip, cut to length and 
solder in the usual way. Alternatively 
lay strip over the holes and using a 
drawing pin or scriber prick a Hole 
In the ‘Cir-Kit* in the required 
position. 


Xir-Kit' strip can be bent or curved 
to whatever form you require and 
used on either or both sides of the 
boa~d. When joining two pieces of 
Xir-Kit’ bend over the end of the 
overlapping strip so that a metal to 
metal contact is made and solder in 
the usual way. 


M«tf« In th« u.k. 


SIZES: 1 / 8" and 1 / 16" WIDTHS 

Length: 100 ft. roll, 5 ft. card 

IDEAL FOR PROTOTYPE AND PRODUCTION 
CONSTRUCTION 

USEFUL FOR WIRING REPAIRS 

e NO DRILLING e FAST e NO MESS 

Available from all Leading Radio Houses 


Marketed by— 


ZEPHYR 

PTY 


PRODUCTS 
. LTD. 


70 BATESFORD RD., CHADSTONE, VIC., 3148 
Telephone 56-7231 



Manufacturers of Radio 
and Electrical Equipment 
and Components 


New All 

Ilf— Silicon 

e 30 / 60W PA 

W —* PORTABLE 
AMPLIFIER 

12 16V, two inputs, 5mV and lOOmV. 
Dimensions 6VjinW x 3’/4in H x 8V 2 in D. 15 
ohm output. No 763D, $62. For 125, 250, 500 
Ohm output. No 763A, $64. For 240V 
operation $33 extra. 

10W PA amplifier similar to above, 4-ohm 
output, 240V operation. No 729D, $40. 
Freight extra. 

CD IGNITION COIL 

For EA (Fraser) circuit. Mounted on 
strong fibreglass printed circuit coded for 
all other components. Polyester film layer 
insulation. Connected and tested. For 
standard distributor, No 787, for photo cell 
distributor, No 786. $8 each. Postage 20c 
each. 

R.C.S. COMPLETE 
DO-IT-YOURSELF 
KITS 

Peak reception. 
Low price. No ex 
pensive test equip 
ment. Everything 
fits. 1964 RF Trans 
porta 7. 

Complete kit — No ^40 - $43.50 

Portable car radio. Identical to 640 above, 
plus extra switch and car coil, etc. No. 

642 $46.00 

Postage $1. 

(Write for booklet on 640 and 642.)_ 

NEW TRANSISTOR PREAMP KIT 

SIZE 3 x 2 x lin, 2 req. for stereo. 

LOW IMP input, 2 trans, 672C $6.50 

Wired ready for use, 672D $8.00 

HIGH IMP, 2 trans, 680C $6.50 

Wired ready for use, 680D $8.00 

HIGH IMP silicon, 3 trans, 682C $8.00 

Wired ready for use, 682D $9.50 

Postage 10c each. Write for data. 

COILS and IFs 455KHz 

Aerial, RF,Oscand IFs $2.00 

Ferrite aerial $2.40 

No 265 Universal tape Osc coil $6.00 

Postage 10c. Write for details and price. 




HI-FI BROADCAST 
TUNER UNIT 
4 TRANSISTORS—HIGH 
SENSITIVITY 

RF mixer, IF, power detector stages, adjustable aerial coupling. 
Complete as illust, wired and tested with 461 dial, knobs and switch 
pot, No. 474D, $31. Freight extra. 

WHISTLE FILTER for above set for 8KHz bandwidth. (Can be 
altered to9,10or llKHz.) No. 128, $4. Post 10c. 



10W STEREO 

MULLARD 
10 -I- 10W RMS 

With output transistor PROTECTION. Frequency 
response 40Hz to 30KHz. Distortion 0.5 per cent. Treble, 
bass boost, 20dB. 

Complete kit of parts. No. 480C $74.00 

Wired and tested, No. 408D $79.00 

Cabinet as illustrated extra $10.00 

Magnetic pickup preamp, No. 762D extra $11.50 

Inbuilt BC tuner with w filter extra $35.00 

Plus freight. Write for brochure. For special Saturday 
demo, ring.59 6550. 


PRINTED CIRCUITS 

Clearly coded for easy assembly. With blueprint parts list. 
Immediate despatch. Add 20c postage. (Specials to your 
drawings.) Write for complete list of all printed circuits. 


813- ET.Ol1 

814- 71.T12 

815- ET.007 
81 7-ET.014 

818- ET.01 7 

819- ET.018 

820- ET.019 

821- 71.C12 

822- ET.022 

823- 72.SA1 

826- 72.T2 

827- ET.021 

828- ET.023 

829- 72.T 2D 

830- 72.R2 


1.80 

3.00 

2.30 

2.50 

2.50 

2.50 

2.50 

4.00 

2.50 

3.00 

4.00 

2.50 

2.50 

2.00 

2.50 


831- 72. 

832- 71., 

834- ET, 

835- 72. 
767-70.1 
777-70. 
788-71. 
772-70. 
663-64. 
579-64. 

683- 64. 

678- 65. 

679- 65. 

684- 65. 

685- 65. 


P3 2.00 
A8 2.50 
026 2.50 
T 3 2.80 
BF08 2.00 
F10 2.00 
03 2.00 


G 7 
M7 
A8 
A9 
09 
M9 


2.00 

2.50 

2.50 

2.50 

2.50 

2.50 


P10 2.50 

P12A 2.50 


686-65. P12B 
694 66.R2 
704-67. P2 

707- 67.P3 

708- 67.A3 

709- 67.P4 
71 1-67.A4 
723-68.5T 
731-68.M12 
736-69.5T 
750-70-A1 
756-70.R 1 
758-70.PI 
778-70.TX2 
792-ET.003 


2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.50 

2.5C 


726- 68. 
759-70. 
776-70. 
717-68. 

741- 69. 
74 7-69. 
746-69. 
669-65. 

727- 68. 

728- 68. 
734-69. 
738-69. 
740-69. 

742- 69. 
748-69. 
754-69. 


2.80 

2.80 

4.00 

3.00 

3.00 


CIO 3.00 
P9 3.00 


3.20 

3.20 

3.20 

5.00 

5.00 


1OCL 5.00 
C9 5.00 
DIO 5.00 
Cll 5.00 


I 


TRANSFORMER 

Tap 6V and 9V at 100mA. 

Filter capacitors, rectifier, resis¬ 
tor, etc. $6.50. Post 20c. 



NEW STEREO MAGNETIC PREAMP 

Hum free, 5mV input, 250mV out. Size 3 in 
x 2in x lin. Wired ready for use. No. 762D. 
$11.50. Post 10c. 


NOISE FILTER 

for radio and TV 

No 27 line filter, 2A $8.50 
No 29, 10A. No. 29B, 20A 
line filter $35 

No 30 pulse filter, 2A 

$11.50 

No 11 aerial filter $13 

Order direct. Pack and post 50c. 


MAGNETIC STEREO PRE +AMP 

In 5mV, out 250mV. Bass and treble 20dB. 

No 724C *29 

Wired ready for use $31 

Postage 30c each. 

For crystal, ceramic. No 722D $27 

NEW BASS BOOST 
4-TRANSISTOR STEREO AMP 
Unity Gain: 

400Hz, OdB Connect between your 

100Hz, 5dB preamp and main amp. 

50Hz, 9dB No 7910, $10.80. 

30Hz, 14d B Postage 20c. 


779- 70. R.D.l 

780- 70. P. A. 1 
790—70.H.P.1 
783-71.T.U.2 

766-773-789-71. R.l 
796-71.S.A.4.A 

798-71.S.A.4.C 
770—71.A.8 
812-71.P.8 


$3.00 
$3.00 
$3.00 
$2.00 
$2 ea. 
$2.50 
$2.50 
$3.00 
$2.50 
$2.50 


n £ Order by Mail Order. Postal Note or Money Order (add post) direct to — 

K.C.5. radio PTY. LTD., 651 FOREST ROAD, BEXLEY, N.S.W. 2207. 587 3491 


104 


ELECTRONICS Australia, June, 1972 


































ELECTRONIC CONSTRUCTION KIT 

New kitset offers a valuable beginning for intending electronics students 
and hobbyists. 


Before this reviewer examined the Radionic kitset, 
he expected to find a toy, which would eventually end 
up all over someone’s backyard. However this kitset is 
not a mere toy. It would appear to be aimed at the 12 to 
16 year old market, but no doubt new enthusiasts with 
many more years behind them would also enjoy 
constructing and testing some of the 33 interesting and 
functional projects. 

With the kitset comes a 111 page manual. The first 8 
pages describe the kit and the function of each com¬ 
ponent in detail. Half of the remaining literature 
covers the 33 experiments, with detailed circuit 
description of each, including sucf) basics as acceptor 
and donor impurities, electron-hole pairs etc. The 
remainder of the manual covers “Fundamentals of 
Electricity”. 

The main part of the kit is a printed wiring board, 
with >/m inch diameter holes drilled at each connecting 
point. Each component is mounted on a moulded 
plastic base with two or more screw studs projecting 
from the other side for assembly and connection. With 
the component mounted on the conductor side of the 


board, 6BA nuts and washers (supplied with the kit) 
are used to ensure that the component is secured in 
circuit. No solder or hook up wire is necessary. 

Components supplied include: two transistors, a 
diode, a light dependent resistor, a variable capacitor, 
a sjx volt lamp and holder, an earphone, a ferrite rod 
and MW coil assembly, seven capacitors, seven 
resistors, a morse key, a length of copper wire (for 
extra coils) and battery connectors. There is no bat¬ 
tery supplied but standard PP4, PP7 or PP9 types are 
recommended. 

The first project we set up was a moisture detector. 
The two transistors are connected as a Darlington pair 
and a 40mA lamp was placed in the collector circuit. A 
piece of blotting paper with two wires threaded ap¬ 
proximately half an inch apart along the length was 
used as a sensor, in series with a 22k resistor connected 
between the supply rail and the Darlington pair base. A 
small drop of water between the sensor wires soon 
spreads sufficiently to initiate base current, and the 
lamp glows due to collector current. 

We also set up a “safety beacon”, consisting of a 



multivibrator with the lamp in one collector circuit. 
Other projects include: A tuned radio frequency 
receiver, a morse practise set, a time switch, an 
electronic violin ana 27 others. 

We were very impressed by the Radionics X30 Radio 
and Electronics Kitset, and would recommend it as a 
suitable beginning for any youngster — or oldie — keen 
to start in electronics. The kitset is distributed by 
Ferguson Agencies Pty Ltd, 562 Swanson Street, 
Carlton, Vic 3053, or 125 Wright Street, Adelaide, SA 
5000. (G.N.) 


CRC INDUSTRIAL CHEMICALS 


CRC Chemicals Australia Pty Ltd announce that they now have a complete 
range of chemicals for use in engineering, electrical and electronic, 
automotive, and marine applications. They also provide an advisory service 
for all sections of industry. 


A number of these products are of particular interest 
to the electrical and electronics industry. CRC 2-26 is a 
moisture displacer, useful on wiring and windings 
affected by water or humidity. It also has anti¬ 
corrosion, penetrating and lubricating properties. 

CRC Lectra-Glean is a heavy duty cleaner and 
degreaser. It is non-flammable and non-toxic but may 
be used in most applications previously requiring toxic 
substances such as carbon tetrachloride. 

The company’s CO Contact Cleaner is a powerful 
fluorocarbon solvent which is non-flammable, non- 
toxic, and safe on, almost all materials. Being highly 
volatile it leaves no residue, and may be used on relay 
contacts, tape recorder heads and similar delicate 
components. 

Urethane Seal Coat produces a fexible durable film 
for use on insulators, electrical windings, printed 
wiring boards, TV feeder cables etc. It is particularly 
useful out of doors in areas subject to heavy salt or 
industrial contamination. 

Rapid Freeze is a freezer aerosol for rapidly cooling 
individual components suspected of being temperature 
sensitive. It is invaluable for quickly locating in¬ 
termittent faults which may otherwise require hours of 
costly time to track down. 

One of the more recent additions to the CRC range is 
3-36. This is generally similar to 2-26, but has been 
specially compounded for the engineering industry, 
rather than the electrical industry. As with 2-26 it is a 
moisture displacer with anti-corrosion, penetrating 
and lubricating properties. 

As already intimated, there is a wide range of other 
products of interest to mechanical, electrical and 
marine engineers. 

The company’s advisory service can make 
available, in the first instance, detailed technical data 
sheets describing these products, their uses and 
manner of application, plus sample aerosols of the 
selected product. Such requests should be made on 
company letterhead. 

In the event that the problem is a more difficult one 


IRH POTS . . .from P. 103 


the company can provide on the spot technical advice. 
This service is available in all states. 

For further details contact Mr John R. Nicholson, 
National Sales Manager, CRC Chemicals Australia Pt; 
Ltd, 209 Bulwara Rd., Pyrmont, 2009. 


TRADE RELEASES — in brief 

ELCOMA DIVISION, Philips Industries Ltd, GPO 
Box 2703, Sydney, 2001. Polystyrene capacitors, 
Micropoco range. These are of extended foil con- 
truction with the leads bonded to all foil layers. This 
virtually eliminates the risk of intermittent faults and 
results in very low inductance. Current stocks com¬ 
prise a 125V range supplemented by some values from 
other voltage ranges. The 125V range encompasses 
preferred values from 560 to 3900pF. Initial stocks are 
limited to 5% tolerance types. Operating temperature 
range is from -40 to +85*C. 

SCHLUMBERGER INSTRUMENTATION AUST 
PTY LTD, PO Box 138, Kew, Vic 3101. Agent for Heath 
Co, USA. Heathkit communications receiver, model 
GR-78. Frequency coverage: 190 to 410kHz, and 0,.55 to 
50MHz in five bands. Powered by 9.6V %??MAh nickel-, 
cadmium rechargeable battery, with in-built trickle 



charger. All solid-state design including FETs. Modes: 
AM, CW and SSB. Features: bandspread tuning; 
automatic noise limiter; relative signal strength 
meter; receive/standby switch; muting connection; 
built-in 500Hz crystal calibrator; double superhet on 
highest frequency range. 


from 1 ohm to 25k, linear law only, with standard 
tolerance of 10% (special .5%). They are rated at 
3W at 25*C derating to no load at 105" C. The voltage 
rating is 1000V AC for one minute, bushing to ter¬ 
minals,. and 500V DC (load not exceeding wattage 
rating) across end terminals. 

Full technical details of the AW series may be ob¬ 
tained from IRH Components Pty<Ltd, The Crescent, 
Kingsgrove, NSW 2208. 


MOTOROLA SEMICONDUCTOR PRODUCTS, Suite 
204, 37-43 Alexander Street, Crows Nest, NSW 2065. 
Zero-voltage switch, type MFC8070. Designed for zero- 
voltage gating of triacs, the MFC8070 can be used to 
drive resistive loads in noise sensitive environments. 
Features: internal input short or open circuit 
protection; built-in voltage regulator for operation 
from AC line; peak output current at least 50mA into 40 
ohms; rated power dissipation 1W at 25 C; operating 


temperature range -10 to -1-75 C. 

A differential input allows two external sensors to be 
comparet to a reference voltage to generate or inhibit 
the output gate pulse. Switching threshold is typically 
within 10m V of the reference voltage. If the differential 
input capability is used, zero-voltage triac gating 
applications can be expanded to include hysteresis 
effects and proportional control. 

ROYSTON ELECTRONICS PTY LTD, 22 Firth 
Street, Doncaster, Vic 3108. Agent for Film 
Microelectronics Inc, USA. Input / output hybrid ICs. 
Three basic units — to provide analog-to-digital and 
digital-to-analog interfacing — are available: quad 
current driver, quad DC interface, and dual level 
shifter. 


TAPE RECORDER & 
HI-FI AMPLIFIER 
SERVICE BY 

QUALIFIED ENGINEERS 


J. 


WALLY SHAW 


29 ALMA ROAD, 
ST. KILDA, VIC. 


Trade enquiries welcomed 
94 2742 



SOUND HOUSE 


“BARAC” 

CARBON FILM RESISTORS 

All values and tolerances now 
available ex stock. 

Manufacturers and Distributors 
invited to send for samples and 
specifications. 

SOUND HOUSE PTY. LTD. 
AUDIO CONSULTANTS 
14 BEATTY AVE.. ARMADALE. 

VIC. 3143 - PHONE 20 6069 


ELECTRONICS Australia, June, 1972 


105 


























At last a breakthrough in the cost for high 
quality portable radio transceivers of the 
walkie-talkie hand-held type. We are 
introducing and offering for sale a fully 
PMG approved 

MIDLAND 1 WATT TRANSCEIVER 

for 27,240KHz operation with switch 
provision for two additional channels, 
tone call signal, background noise 
sguelch control, battery voltage in¬ 
dicator, steel case with separate cover, 
good for five miles distance com¬ 
munication under average field con¬ 
ditions, with penlite cell-batteries for 
ONLY $39.95 PER UNIT, FULLY GUARANTEED. 


MAGNAVOX WIDE RANGE TWIN CONE SPEAKERS 

8 or 16 ohms VC. Post and Packing 65c. 

6WR MK V 12 Watts RMS $9.90 
8WR MK V 16 Watts RMS $10.75 
10WR MK V 16 Watts RMS $11.50 
12WR MK V 16 Watts RMS $12.50 


SPEAKER SPECIAL 

Imported Tesla 8” Speakers. 8 
ohm imp. $4.75. Post and Packing 
65c. 


NEW IMPORTED STEREO TURNTABLE AND PICK-UP 

240 VOLT AC 3 speed turntable with ceramic 


OPERATION 



stereo pickup counter-balanced 
tubular arm, $7.90. Base in teak 
or walnut, $5.50 extra. De luxe 
base $8.50 Post 50c or $1.00 with 
base. . 

Turntable and motor separate .. $4.50 


A TRANSISTOR PREAMP FOR MAGNETIC 
PICKUP OR TAPE HEAD 

Using 2 transistors per channel, as featured in “Electronics 
Australia” (Sept. 1971). Complete kit includes transistors, PC 
board, resistors, capacitors. 

Circuit and full details supplied. 

Kit (not incl. box) $7.90 
240V Power Supply $4.50 
Metal box $2.00 extra. 

State if required for pickup or tape 
head. 



NEW LOW COST STEREO SYSTEM 

AS FEATURED IN JAN. ELECTRONICS AUSTRALIA 
Complete kit of parts including “Garrard” 
record player with auto, stop and crystal 
pick-up. Magna vox 8WR or 6WR wide range 
twin coned speakers. (Cabinets not sup¬ 
plied). Amplifier only, less speakers and 
player. $32.00 
$69.50 Post and packing $2.50 extra. 



POLYESTER CAPACITORS 

Pack of 100 new polyester capacitors .001 to 0.1 in 160, 250 and 
400 volts working. $3.50 Plus 50c Post and Packing 


BROADCAST TUNER KIT 

$22.50 

Post 75c. 

Complete kit of parts including dial mechanism and zener 
diode for this I.C. tuner as featured in Feb. 71 E.A. _ 



NATIONAL RADIO SUPPLIES 


332 PARRAMATTA ROAD, STANMORE, NSW 2048 PHONE 56 7398 



KONTAKT Kalte (Cold) 
Spray 75 can quickly isolate 
thermal faults in semi¬ 
conductors, condensers, re¬ 
sistances and similar com¬ 
ponents. 

Invaluable for the service 
technician, Kontakt 75 is a 
non toxic, non inflammable 
and chemically inert coolant 
spray which can produce 
temperatures down to —42° 
Celsius. 

Other Uses include:— Pre¬ 
vention of heat damage 
during soldering. 

Location of tiny flaws such 
as hairline cracks which 
cause faulty operation when 
the component becomes 
heated. 

Rapid cooling or freezing 
of laboratory specimens. 
Quick return of heated 
instruments, etc. to ambient 
temperatures. 

SOLE 

AUSTRALIAN 
AGENTS 

ADELAIDE BRISBANE HOBART 
MELBOURNE PERTH SYDNEY 


H. ROWE 


ELECTRONICS Australia, June, 1972 


106 



















AMATEUR BAND 
NEWS AND NOTES 

by Pierce Healy, VK2APQ 

Proposed New Licence Structure 

The Wireless Institute of Australia is to seek,from the Postmaster-General’s 
Department, a four class licence structure for the Australian Amateur 
Service. If approved, it is hoped that it will provide a substantial boost for 
the amateur ranks. 



Featured in these notes from time to time has been 
the need for a “novice type” licence for the Australian 
Amateur Service. During the past four years the 
opinions of many interested persons have been 
published, including the recommendations of a com¬ 
mittee which investigated the subject. 

As recently as March, 1972, details of a sup¬ 
plementary report prepared by a WIA committee were 
published. That report was the basis for discussion at 
the WIA federal convention in Melbourne over the 
Easter, 1972, weekend. 

Following this, an official statement was made on 
Sunday morning, 9th April, over all WIA divisional 
stations. This set out the WIA policy. 

"The institute now has a policy of seeking a four 
class licence structure from the PMG’s Department. 
The old terms ‘Full’ and ‘Limited’ licences would 
disappear under the proposed system and the terms 
‘Grade A’; ‘Grade B’; ‘Grade C’ and ‘Grade D’ would 
replace them. 

“Briefly, the different grades would be as follows:— 

“ ‘Grade A’ — formerly the AOCP, with all 
qualifications and privileges as at present. 

“ ‘Grade B’ — regulations and theory examinations 
as for Grade A, with a five word per minute Morse code 
(CW) test. Operation permitted on all amateur bands 
21MHz and above using all modes of transmission 
permitted for Grade A. The holder of a Grade B licence 
may convert to Grade A at anytime on passing the 
lOwpm CW test. 

“ ‘Grade C’ — Formerly the AOLCP, but future 
AOLCP holders would be licensed to operate only on 
144MHz and above. Grade C licence holders may 
convert at any time to Grade A or B by taking the 
appropriate CW examination. 

“Present AOLCP holders would retain their existing 
privileges. 

“ ‘Grade D’ — regulations as for Grades A, B and C, 
but a lower level theory examination and a 5wpm CW 
test. Privileges would be; Crystal controlled trans¬ 
mitter, 10 watts input to the final stage and CW mode 
only. It has been recommended that frequency sub¬ 
allocations 21.075MHz to 21.15MHz and 28.1MHz to 
28.2MHz be allotted. The licence to have a two year 
tenure after which time the holder must convert to 
either Grade A or Grade B or the licence shall lapse. 

“These are the recommendations made by Federal 
Council last weekend. The council also directed that a 
review of the effect of the ‘D Grade’ licensing system 
be carried out after a period of five years from the date 
of inception.” 

It was stressed in the broadcast that these were WIA 
proposals which may or may not be acceptable to the 
Postmaster-General’s Department. 

What are the main differences between this policy 
and the scheme envisaged by the investigating com¬ 
mittee? Very little change fras .been made in what is 
now termed “Grade D” licence. The differences are: 

a. The bands on which operation be permitted has 
been reduced to two HF bands (21MHz and 28 
MH-z) with slight reduction in sub-band limits. 

b. The tenure of two years for such a licence. This 
was suggested in the original report but was 
amended to no time limit in the supplementary 
report. 

It was envisaged that holders of the AOLCP licence 
would, on passing a CW test at novice licence standard, 
be granted the privileges of both. This standard is now 


termed “Grade B”. 

The difference between the present AOLCP and 
“Grade C” is the loss of the 52MHz band by future 
holders. This change would remove an anomaly, in 
that International Telecommunication Union 
regulations require that Morse code be a requirement 
for amateur licences for the 52MHz band. 

There should be little doubt that the proposal will be 
given favourable consideration by the PMG’s 
Department. It has been publicly stated that: — “the 
Department would be pleased to examine any fresh 
proposals relating to novice licences should the in¬ 
stitute seek to have the subject submitted for further 
consideration” (“EA” August, 1971, P83). 

A point that should be emphasised concerning the 
proposed review period is that, besides being a self 
educational activity, amateur radio is also a self- 
disciplined activity. In each state a committee of 
representatives of the amateur service and PMG’s 
Dept officers meet regularly to consider reports 
concerning breaches of regulations or other matters. 
Should the proposal be accepted, the activities of those 
licensed under the new system would be closely ob¬ 
served and where necessary guided towards the 
correct operating methods and on air behaviour. 

QCWA MEETINGS 

The Sydney Chapter of the Quarter Century Wireless 
Association had a change of venue for their meeting on 
8th March, 1972. Twelve members met for dinner at the 
RSL Memorial Club, North Sydney. 

On Tuesday evening 14th March, 13 members 
were guests at an inspection of the Postmaster 
General’s Department monitoring station, Middle 
Head. 

Two officers of the department, Bill Clarke and Chas 
Hurndell, were the hosts. The station is the standards 
establishment for radio frequency measurements in 
the Commonwealth of Australia and comes under the 


In addition to licensing, several matters relating to 
VHF and HF operation were discussed at the WIA 
Federal Convention during Easter, 1972. These include 
VHF UHF band planning, especially in the 144MHz 
band; repeaters; project Australis, the use of GMT, 
and WIA contest awards. 

It was decided that the Victorian Division would 
provide the personnel for a federal VHF UHF band 
planning advisory committee. This committee to work 
in close co-operation with other federal committees 
and interested parties. 

The repeater committee, provided by the NSW 
Division since its inception in 1968, was reappointed for 
a further three years. A recommendation was adopted 
that no repeater or simplex net channels be set up 
below 146MHz until agreement has been reached on 
VHF UHF band planning. 

Regarding contests, charges have been increased for 
non-WIAmember applicants for the following awards: 

Australian DXCC 

Australian VHFCC 

Australian WAS 

TTie VHFCC award has been extended to cover UHF 
and SHF. Also the WAVKCA now has its counterpart 


jurisdiction of the Frequency, Regulatory and 
Licensing, Radio Section; Engineering Division, 
Postmaster-General’s Department. 

During the two hour inspection the visitors were 
given practical demonstrations of the methods used to 
measure the frequencies of HF and VHF radio trans¬ 
mitting stations in both the commercial and amateur 
services. 

The equipment in service was described and the 
procedures used were explained. The visitors were 
very impressed with the accuracy which is achieved 
and the magnitude of the task of monitoring local and 
overseas transmissions. It was pointed out that co¬ 
operation received from foreign administrations in 
eliminating interference to various radio channels due 
either to propagation effects or other factors was of a 
very high order. 

To their hosts for the evening and to Mr Ron Holt of 
the Radio Branch, Sydney, members who attended 
express their appreciation for a very informative and 
educational evening. 

Membership of the Sydney Chapter, QCWA, is open to 
amateur radio operators who have been licensed for 25 
years or more. Further information may be obtained 
from the President, Harry Caldecott, VK2DA; 
Secretary, Pierce Healy, VK2APQ; Treasurer, Brian 
Anderson, VK2AND at their call book addresses. 

The guest at the April meeting was Ron Holt, 
VK2QQ, of the Radio Branch PMG’s Dept, Sydney. 
During the informal discussion following dinner, Ron 
spoke on the work done by the monitoring station and 
outlined some of the tasks undertaken by the Radio 
Branch in conjunction with other members of the In¬ 
ternational Telecommunication Union, Frequency 
Registration Board (FRB). 

Visitors also present at the April meeting were: Ivan 
Agar, VK2AIM and A1 Davis-Rice, VK2AXR. 

AMSAT NEWS 

Last month’s notes mentioned possible delay in 
launching the A-O-B amateur satellite. Official in¬ 
formation has confirmed the delay, caused through 
some systems falling behind schedule. The AMSAT 
Board of Directors has decided to prepare a more 
simplified space craft to meet the launch date in July, 
1972. This will be known as A-O-C. Details are :— 

Weight — 35 pounds (15.876kg) 

Dimensions — 17” X 12” X 6” (43 cm X 30cm X 15cm) 

Structure — Non-modular 

Power 

Solar panels — 50% of surface 

Voltage — 24 volts 

Battery 6A hr — 18 cell nickel-cadmium 

Average power — 3.5 watts 
Telemetry — 24 channel Morse code format 
Message storage — 768 bit programmable shift 
register 

Experiment control — 2 modes, ground controlled 
Command — 21 pulse commands 
Repeaters — 144MHz up 29MHz down, linear, 1-2W 
pep 

Beacons — 29.45MHz (in band beacon within repeater 
pass band) 0.2 watt (A-l); 435.1MHz 0.35 to 0.45 
watts (a-l) 


for the VHF bands. GMT will be introduced into the 
Ross Hull Contest to overcome difficulties caused by 
daylight saving. 

Project Australis was reviewed and additional 
finance approved. Certain proceedures in relation to 
the administration were set down. 

Howard Rider was appointed WIA special 
representative in Indonesia. He will be asked to in¬ 
vestigate and report on how best the WIA may assist 
amateur radio in that area. 

NEW SOUTH WALES 
VHF & TV Group 

The revised charter of the NSW, VHF-TV Group, 
approved by the VK2 Division Council late in 1971, was 
designed to provide a more stable control of the 
group’s activities. Tlie charter now requires that 
nominations for the management committee be 
received in writing at least 21 days prior to the annual 
general meeting. Only six nominations were received 
and therefore no ballot was necessary. The committee 
met for the first time on 13th April, 1972, and the 
following office bearers were elected. 

Ian Binnie, VK2ZIU, Chairman and Treasurer. 

Grahame Wilson, VK2ZGW, Vice-chairman; 
Disposals and Social activities. 

Mike Farrell, VK2AM, Secretary. 

Roger Harrison, VK2ZTB, Public Relations and 
Newsletter Editor. 

Syd Griffith, VK2ZYD, VHF Broadcasts 

Stephan Kuhl, VK2ZSK, Committee member. 


Radio clubs and other organisations, as well as individual amateur operators, are cordially in¬ 
vited to submit news and notes of their activities for inclusion in these columns. Photographs 
will be published when of sufficient general interest, and where space permits. All material 
should be sent direct to Pierce Healy at 69 Taylor Street Bankstown, NSW 2200. 


WIRELESS INSTITUTE ACTIVITIES 


ELECTRONICS Australia, June, 1972 107 













Mid-winter Field Day 

Dates: 

10th, 11th and 12th June, 1972 
Duration: 36 Hours 
Sections: 

l.Single operator stations. Total or six hour periods. 
2. Multi-operator or club stations. Total or six hour 
periods. 

Scoring: 

One contact per band per station per hour, no contacts 
allowed through repeaters for scoring purposes. 

Points may be gained on the following basis 
52MHz & 144MHz bands — 1 point per 10 miles or part 
thereof. 

432MHz band — 2 points.per 10 miles or part thereof. 
Other UHF bands 5 points per 10 miles or part thereof. 
Multiplers: 

Home station — Home station X 1 

Home station — Field / Mobile station X 2 

Field Mobile station — Field / Mobile station X 5. 

The total band score shall be divided by the DC 
power input to the final stage of the transmitter. 

Net Channels: 

Contacts on net channels may claim multiplier points 
only. No mileage points may be claimed. 

Entry forms must be submitted to the secretary, 
VH-F / TV Group 14 Atchison Street, Crows Nest 2065, 
by 28th July, 1972. 

Plans are in hand for a national VHF — DX contest in 
August, 1972. This will be on the same lines as the 
VK8AUcontest (Detailsin “E.A” May 1971, page 139). 

Meetings of the VHF — TV Group are held on the 
first Friday in each month at Wireless Institute Centre, 
14 Atchison Street, Crows Nest, at 8pm. Visitors are 
welcome. 

WIA YOUTH RADIO SCHEME 
Maitland Radio Club 

The club is now providing six technical classes of 
instruction for members of all age groups wishing to 
improve their knowledge in radio and to gain their 
amateur licence. 

Classes held each week include three elementary 
classes for beginners, one junior, one intermediate, 
and the AOCP for advanced members. Instructors are 
Messrs D. Cross, K. Mahon, A. Counsell, J. Gibson, K. 
Watson. 

As the club’s major building program is completed 
the newly elected committee is building up tool kits and 


electronic projects to promote the practical in¬ 
struction. The committee has made certain class 
projects compulsory for the Youth Radio Club 
Scheme’s radio certificate examinations. 

The club is located in Maize Street, Tenambit, East 
Maitland. Details may be obtained from the secretary, 
PO Box 54, East Maitland 2323, or telephone Maitland 
33 7286. 

Westlakes Radio Club 

The club has now installed its VHF transmitter at 
its new location, Church of England Hall, Ranclaud 
Street, Booragul. It will be used as part of the in¬ 
structional course for the AOCP and AOLCP classes. 
The tower carrying the VHF antenna, erected at the 
rear of the building will also be used as support for the 
inverted “V” aerial for 160 metres. This together with 
a HF transmitter will be used for instruction. 

Details of the club may be obtained from the 
secretary, Eric Brochbank, VK2ZOP, PO Box 1, 
Teralba 2284 or telephone Newcastle 58 1588. 

St George Amateur Radio Society 

The St"George YRCS Training Annex continues to 
attract attention and praise for its audio-visual in¬ 
structional program. 

A students’ council has been formed among those 
studying at the annex, and invited to submit 
suggestions for further improvements. One suggestion, 
already being examined by the education officer, Noel 
Ericsson VK2MF, is the establishment of a Saturday 
afternoon workshop training program. 

A Morse code trainer is now operative and ex¬ 
perience has shown that a student can learn to receive 
the code at three words per minute in six weeks. Stan 
Clark has joined the construction team which is 
building an electronic coupling unit which will enable 
fully automatic presentation of the audio-visual 
programs. 

Details may be obtained from Noel Ericsson, 
VK2-MF17 McIntyre Avenue, Brighton-le-Sands, 2216 
or telephone 59 1658. 

To cater for society members who possess a 
knowledge of fundamental radio theory, Mike 
McKenzie, VK2BMM and Chris Jones, VK2ZDD have 
organised an AOCP preparatory class each Tuesday 
night. To cater for the holders of limited licences and 
others who can receive Morse code at 5 words per 
minute, Alf Cutting, VK2AAC and Ivan Brown, VK2RY 




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conduct a training session each Thursday night. For 
details of venue phone Mike McKenzie, VK2BMM, on 
299 2920. 

Club meetings are held in the Civil Defence Hall, The 
Mall, South Hurstville, on the first Wednesday of each 
month. Visitors welcome. 


Springwood Bush Fire Brigade 

Training classes for YRCS and AOCP examinations 
are being conducted in the Springwood district, within 
the Springwood Bushfire Brigade, under the super¬ 
vision of Rex Black, VK2YA. Although most of the 
students are drawn from the Brigade, the classes are 
open to all. 

Five adult members of the Brigade communications 
group attended the February Amateur Operators 
Certificate of Proficiency examination conducted at 
Springwood Civic Centre by the Postmaster from 
Lawson. At the subsequent “post mortem” it appeared 
that there could be two or three successful candidates. 
The official results are awaited with interest. Only two 
attempted the Morse code test and it seems that they 
might have to try again at the May Morse code test. 

However, it will be possible for them to concentrate 
on the Morse code without the distraction of studying 
the theory and regulations. So this year should see 
several more Full AOCP operators pouring RF into the 
ether from the Blue Mountains area. 

Several adult and school student members of the 
North Springwood Fire Brigade have already been 
successful in obtaining their YRCS Elementary Radio 
Certificates, these are:— 

Honours Pass: Bruce Farnsworth, John Oxley, 
David Noble, Les Begg. Pass Grade: Pat Hanvin. 

Meetings of both AOCP and YRCS groups are held in 
the Fire Tender shed at North Springwood. The ,4 red 
monster” has to be moved out to make room for the 
radio students. It is hoped that one day a separate 
communications centre including an amateur radio 
station will be available so that supervised operating 
instructions may be given to the enthusiastic mem¬ 
bers. 

One of the aims of the organisers of the Springwood 
group is to provide personnel trained in radio com¬ 
munication who would be available in the case of bush- 
fires which can do a great deal of damage in the area. 


Central Coast Repeater 

To enable users to obtain the most satisfactory 
performance from the Central Coast repeater the 
following information has been made available by the 
repeater committee of the Central Coast Amateur 
Radio Club. Installed at the club rooms located at 
Kariong just south of Gosford, New South Wales, the 
location provides an excellent coverage area, not only 
for the Gosford area but for many miles to the north 
and south for those travelling along the Pacific High¬ 
way between Sydney and Newcastle. 

Operating on Channel I under the club’s official call 
sign VK2AFY-R, the repeater was temporarily in¬ 
stalled for the Field Day held on 20th February, 1972. 

For Channel 1 repeaters the user must transmit on 
146.1MHz and receive on 145.6MHz. Crystal 
frequencies required for the conversion of several 
types of mobile units available through disposal 
sources are: 

Unit type Transmit crystal Receive crystal 

AWA 4058.333KHZ 10257.143KHz 

Pye Ranger 4053.333KHz 13025.0KHz 

TCA 1674 4053.333KHZ 20514.285KHZ 

TCA 1675 / 77 4058.333KHZ 42948.0KHz 

Some STC 6087.5KHz 16600. OKHz 


The receiver of the repeater operates continuously 
but the transmitter is only brought into operation when 
it is required to be used. If the transmitter is not heard 
in operation it is necessary to transmit a steady, un¬ 
broken, preferably flutter free carrier into the receiver 
of the repeater for five seconds. Then wait for 40 
seconds for the filaments of the valves in the trans¬ 
mitter to heat up. 

The repeater call sign will then be transmitted in 
MCW at 860Hz tone to signify that the repeater is 
operational. You may now transmit into the repeater, 
but allow half second for the relays in the repeater to 
operate before speaking. When you cease to transmit, 
the repeater will transmit a two second noise burst 
from the unmuted receiver. The purpose of this two 
second hold time is to prevent chopping up (multiple 
keying of the repeater transmitter) on a fluttery signal 
at the repeater input. 

In compliance with the PMG’s Department 
requirements the repeater is equipped with timers 
which automatically turn the repeater off in the case of 
a malfunction. But unfortunately the timers cannot 
identify the difference between a lengthy transmission 
from a user to a fault condition that may occur. The 


108 ELECTRONICS Australia, June, 1972 














first of these timers is concerned with the length of 
transmission into the repeater. 

If a fault condition exists or the length of a single 
transmission period by a user exceeds four minutes 
duration, a two second burst of 860Hz tone is 
superimposed on the repeated audio at low level (15dB 
below clipping level in the repeater transmitter) to 
indicate “Time out” and the transmitter is switched 
into stand-by condition. 

The tone burst indicates to the listener that a “time 
out” has occurred as distinct from a repeater failure or 
a failure in the transmitting operator’s equipment. To 
prevent “time out”, operators should cease trans¬ 
mitting for one second every three minutes to ensure 
against a “time out”. A one second pause should be 
made between overs. It is not necessary to wait for the 
completion of the two second noise buist. 

The repeater call sign, VK2AFY-R will be 
automatically transmitted every four to five minutes 
whilst the repeater is in use. If the repeater is not used 
for eight minutes, or a signal is transmitted into the 
repeater continuously for eight minutes (possibly a 
fault condition), the transmitter power supply will be 
turned off. If the condition is a continuous carrier or 
receiver fault, the carrier or fault must clear to allow 
the repeater to be turned on again. The switch on 
procedure is as previously indicated. 

If the transmitter locks on, ie, remains on after the 
normal two second noise burst period, the repeater will 
operate normally whilst it is used as above, with one 
exception. If a signal is.not received at the repeater 
input for thirty seconds, the transmitter power supply 
is turned off, but may be turned on as previously 
described. 

Further information may be obtained from members 
of the repeater committee or by writing with any 
queries to the chairman, 

Central Coast Repeater Committee, 

Post office Box 238 

Gosford, NSW 2250. 

Please include a 9” x 4” stamped self addressed 
envelope with any inquiry to facilitate the despatch of 
your reply. 


Moonbounce Success 

On Wednesday evening, 19th April, 1972, a successful 
two-way Earth-Moon-Earth contact was made on 432- 
MHz from Dapto, New South Wales, to Inglewood, 
California. 

The stations were VK2AMW (call sign of the 
Dlawarra Branch, NSW Division WIA) operated by 
Lyle Patison, VK2ALU, from the Wollongong College 
Radio Telescope at Dapto and Harley Herndon, 
WA6HXW in Inglewood. Further tests were scheduled 
to be made during May. 

The story of this combined UHF project, by 
amateurs in the Dlawarra area and the Wollongong 
College, were given in the May, 1971, issue of these 
notes. 


VICTORIA 

Geelong Amateur Radio-TV Club 

The April newsletter contained a comprehensive 
questionnaire inviting suggestions and comments 
which would assist clubs activities. This should assist 
the committee to plan activities for the coming year. 

Visitors to Geelong are invited to attend club 
meetings which are held at the Club Rooms, Storrer 
Street, East Geelong, each Friday night. Contact the 
secretary, Bob Wookey, VK31C, PO Box 520, Geelong, 
Vic 3220 or telephone Geelong 212674 for details. 

29 DX CLUB 
VHF RTTY Net 

To encourage and promote interest in RTTY (radio¬ 
teletype) those interested are invited to contact the 
secretary of the 29 DX Club with the view of forming a 
VHF RTTY net. It is claimed that there are more 
RTTY operators in Western Australia than in the 
eastern states. Suggestions should be sent to Alan 
Gibbs, VK6PG, 12 Munyard Way, Morley, WA 6062. 

NEWS FROM INDIA 

At a special meeting, the Amateur Radio Society of 
India and the Radio and Electronics Society of India 
agreed to resolve their differences and form a unified 
amateur radio organisation in India. As from 1st 
January, 1972, a new organisation known as the Radio 
Amateur Society of India, will endeavour to stimulate 
the interest of amateur radio throughout the country. 

Several changes were introduced due to the 
merger. All matters relating to the incorporation of the 


IONOSPHERIC PREDICTIONS FOR JUNE 

Reproduced below are radio propagation graphs based on information supplied by the Ionospheric 
Prediction Service Division of the Commonwealth Bureau of Meteorology. The graphs are based on 
the limits set by the MUF (Maximum Usable Frequency) and the ALF (Absorption Limiting Fre¬ 
quency). They have been prepared for the four most popular amateur bands over a number of 
interstate and international circuits. Black bands indicate periods when circuit is open. 6.72 


7MHz 


EAST 


01 02 03 04 05 06 07 08 09 10 11 12 13 14 IS 16 17 18 19 20 21 22 23 


EAST AUST TO BARBADOS (SR) 

JOHANNESBURG 
McMURDO SOUND 
NEW DELHI 
NEW YORK 
RIO DE JANEIRO 
TOKYO 
VANCOUVER 
WELLINGTON 
WEST AFRICA 
WEST EUROPE (SR) 
WEST EUROPE (LR) 
ADELAIDE TO SYDNEY 
BRISBANE TO MELBOURNE 



SYDNEY 
DARWIN TO SYDNEY 
MELBOURNE TO PERTH 

SYPttEY 


14MHz 


GMT 


15 16 17 18 19 20 21 22 23 24 01 02 03 04 05 06 07 08 09 10 11 12 13 


EAST AUST TO BARBADOS (SR) 

JOHANNESBURG 
McMURDO SOUND 
NEW DELHI 
NEW YORK 
RIO DE JANEIRO 
TOKYO 
VANCOUVER 
WELLINGTON 
WEST AFRICA 
WEST EUROPE (SR) 
WEST EUROPE (LR) 
ADELAIDE TO SYDNEY 
BRISBANE TO MELBOURNE 
PERTH 
SYDNEY 
DARWIN TO SYDNEY 
MELBOURNE TO PERTH 

imm 



21MHz EAST 


01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 


EAST AUST TO BARBADOS (SR) 

JOHANNESBURG 
McMURDO SOUND 
NEW DELHI 
NEW YORK 
RIO DE JANEIRO 
TOKYO 
VANCOUVER 
WELLINGTON 
WEST AFRICA 
WEST EUROPE (SR) 
WEST EUROPE (LR) 
ADELAIDE TO SYDNEY 
BRISBANE TO MELBOURNE 
PERTH 
SYDNEY 
DARWIN TO SYDNEY 
MELBOURNE TO PERTH 

SYPNEY 



28MHz 


GMT 


15 16 17 18 19 20 21 22 23 24 01 02 03 04 05 06 07 08 09 10 11 12 13 


EAST AUST TO NEW DELHI 

WEST AFRICA 
BRISBANE TO PERTH 
DARWIN TO SYDNEY 
MELBOURNE TO PERTH 


new society will be handled by the Radio and Elec- need for a strong International Amateur Radio Union, 

tronic Society of India. The affairs of the Amateur Region 111 organisation. It is safe to predict that when 

Radio Society of India were wound up on 31st the formalities for the transfer of IARU membership to 

December, 1971. Likewise the affairs of the Radio and the new society are completed the RASI will be a very 

Electronic Society of India will be wound up on 30th active member of the Region 111 Association ^ 

June, 1972. w 

The QSL bureau which operated through PO Box 543, 

New Delhi was closed down after 29th February, 1972. 

All QSL cards should now be sent to the Radio and 
Electronics Society of India, PO Box 6538, Bombay 26, 

India until further notice. Any QSL cards received at 
New Delhi after 29th February are sent to Bombay 
for sorting and distribution. 

The publication of the amateur radio magazine, the 
Indian Radio Amateur, will continue to be circulated 
from New Delhi. 

Membership subscriptions should be sent to the 
Radio and Electronics Society of India, PO Box 6538, 

Bombay 26, India until further notice. 

This agreement to reconstitute the official amateur 
radio society of India is the outcome of a decision made 
at the First All India Amateur Radio Convention held 
at Bombay in December, 1969 at which your 
correspondent was a guest delegate. 

Having a first hand knowledge of the problems that 
existed at the time, it is indeed pleasing for me to learn 
that a solution has been found. I feel sure that the 
decision made is a big step in the right direction and 
will greatly assist the rapidly expanding interest in 
amateur radio throughout India. 

The Indian radio amateur is very much aware of the 

ELECTRONICS Australia, June, 1972 109 


SO YOU WANT TO BE 
A 

RADIO AMATEUR? 

To achieve this aim, why not undertake 
one of the Courses conducted by the 
Wireless Institute of Australia? 
Established in 1910 to further the in¬ 
terests of Amateur Radio, the Institute is 
well qualified to assist you to your goal. 
Correspondence Courses are available at 
any time. Personal classes commence in 
February each year. 

For further information write to: 

THE COURSE SUPERVISOR, W.I.A. 

14 ATCHISON STREET, 

CROWS NEST, N.S.W. 2065 













































































































































































ANSWERS TO 
CORRESPONDENTS 


ACT COMMERCIAL STATION: I would like to know 
the opening date for the commercial station in Can¬ 
berra, its name, frequency, power, and the owner. 
(B.H., Deakin, ACT). 

® Although we publish the frequencies, power and 
other information of broadcast and TV stations once a 
year (usually January), we have no information on 
projected stations. We suggest that you contact the 
PMG Radio Branch in your capital city to obtain your 
information. 


TRANSISTOR TESTER: I have built the Transistor 
and FET Tester described in the August, 1971 issue of 
“Electronics Australia”, but I am not clear how to test 
an ordinary PNP or NPN transistor. Does the tran¬ 
sistor have to be in circuit for a test? 1 tried a PNP 
transistor which I know to be good, out of circuit, but 
there was no reaction from the meter. (S.G., Sydney, 
NSW.) 

®The tester is for out-of-circuit checks only. The 
device is connected to the terminals marked E for 
emitter, B for base, and C for collector, in the case of 
ordinary transistors. For FETs, the terminals are 
marked D for drain, G for gate and S for source. If 
appropriate readings are not obtained when the con¬ 
trols are manipulated, and the device tested is known 
to be good, then the tester has a built-in fault which will 
have to be found and corrected. 


COMPLIMENTS: I wish to congratulate you on your 
five simple transistor projects in January 1972. I built 
the white noise generator and the impedance matching 
stage. With the latter inserted between one channel of a 
stereo system and the input to an electronic organ 
(using the organ speaker system for one channel), I 
eliminated a distortion problem, and improved the 
quality greatly. I am looking for more simple projects 
like these. Have you ever published a design for a filter 
system which passes a bass signal only? (N.H., 
Frankston, Vic.) 

$ We are encouraged to know that the simple projects 
you mention have proved of value, N.H., and we are 
glad that you solved you distortion problem with the 
use of one of them. It appears as though the organ input 
was creating this distortion due to loading of the signal, 
and your remedy was quite in order — in fact, we 


probably would have suggested the same type of stage. 
We intend to include more simple projects from time to 
time, so that you should not be disappointed. A filter 
system which passes bass only has not been described, 
but the low-pass section of a crossover network can be 
used if properly terminated in its characteristic im¬ 
pedance. Crossover network designs have been 
published in the Oct 1955, July 1956, and Dec 1956 
issues. Reprints of the above can be obtained through 
the reprint service for 50c each under File Nos 
l/SE/4, l/SE/5, and l/SE/7, respectively. 

NOISE SUPPRESSOR: I am a 14-year-old high school 
student and very interested in electronics. Can you 
help me with answers to the following questions? (1) Is 
it possible to make a noise suppressor for a tape 
recorder output or a suppressor for the input (for 
example, against wind)? (2) What is the formula for 
series resonance, what is a practical way to measure 
impedance, and how does one calcualte the values of 
inductances and capacitances in low-pass and high 
pass filters for given frequencies? (3) Are there any 
devices that give voltage or resistance changes when 
illuminated by ultra-violet light, infrared, or x-rays? 
(C.C., Turramurra, NSW.) 

® Taking your questions in order. (1) If you mean is it 
possible to suppress noise without affecting the signal 
quality, the answer is — No. The second part of your 
question is not clear. However, unwanted ambient 
noise can be minimised by the use of directional 
microphones, and wind noise by fitting a wind shield. 
(2) These questions are all part of basic theory, and the 
answers can be found in just about any good com¬ 
prehensive basic theory book. (3) Such devices do exist 
and are used in various industrial, technical and 
research applications. Articles in ‘‘Electronics 
Australia” often contain reference to devices of this 
nature and their application. 

REVERBERATION: I have been reading your 
magazine for about five years but have not yet come 
across any articles on reverberation units. Any in¬ 
formation available about these units would be useful. 
(W.F., Allambie Heights, NSW.) 

0 We refer you to your October, 1967 copy of the 
magazine where, on page 51, is the start of an article 
describing a reverberation system. However, if you no 


longer have this issue of the magazine, a project 
reprint of the article can be obtained from the In¬ 
formation .Service for 50c (File No l/GA/12). 

TELEPHONE AS AERIAL: I have constructed a 
crystal set using a ferrite rod aerial, and have been 
using the finger stop on the telephone as an aerial. 
Using this I can receive the local station fairly loudly. 
Is there any danger in using the finger stop as an aerial 
or earth? Also, have you published a circuit for a direct 
reading capacitance meter, transistor amplifier with 
high input impedance and 8 ohm speaker, and a 
transistorised metal detector. (J.L., Hamilton. Vic.) 

® While we cannot see any objection to using the 
telephone in this way, there may be something in the 
PMG regulations which prohibits this. You would be 
advised to check up on this with the PMG’s department 
in your capital city. In the modern type of telephone, 
we understand that the finger stop is screwed into 
plastic, and is not part of the circuit in any way. So you 
may have been lucky to have enough capacitive 
coupling to enable the phone to work as an aerial. The 
latest direct reading capacitance meter we published 
was the Probe Type Capacitance Meter, March 1971, 
File No. 7/CM/5. It was for measuring small 
amounts of capacitance, (up to 50pF). An amplifier of 
the type you require was one of the “Simple Transistor 
Amplifier Circuits”, described in the March 1970 issue, 
File No. 1 / XA / 10; and a metal locator was described 
in the January 1970 issue, File No. 3 / MS / 20. Copies of 
these articles are available for the usual fifty cent fee. 


AMATEUR RADIO: Will you please advise me how to 
become an amateur radio operator. (R.P., Ashfield, 
NSW.) 

® The requirements for the operation of an amateur 
radio station are set out in full in the booklet ‘‘Hand¬ 
book for Operators of Radio Stations in the Amateur 
Service”, available from the Radio Branch, Post¬ 
master-General’s Department. 83 Miller Street. North 
Sydney, NSW 2060. The Wireless Institute of Australia 
conducts courses of study for anybody, whether 
members of the Institute or not. who wishes to prepare 
for the PMG examination which applicants for an 
amateur licence must pass. Details are available from 
The Course Supervisor, WIA, 14 Atchison Street, 
Crows Nest. NSW 2065. 


"ELECTRONICS AUSTRALIA'' INFORMATION SERVICES 


As a service to readers Electronics Australia” is able to offer: (1) Project 
reprints metal work dyelines, photographs, printed wiring patterns and 
other filed material to do with constructional projects and (2) A strictly 
limited degree of assistance by mail or through the columns of the 
magazine. Details are set out below 

PROJECT .REPRINTS: These cost 50c per project. Prior to December 
1959, circuits and diagrams only are available. From December 1959 
onwards, complete articles are available No material can be supplied, 
additional to that already published. Reprints can be supplied more 
speedily if they are positively identified and not accompanied by technical 
queries. Material not on file can normally be supplied in photostat form at 
30c per page. 

SUBSCRIPTIONS, BINDERS, HANDBOOKS etc: These are handled by 
seperate departments. For fastest service, send separate orders to the 
departments concerned. 

PHOTOGRAPHS, METAL WORK DRAWINGS: Original photographs are 
available for most projects. Price: $1 for 6in x 8in glossy print. Metal work 
dyelines are available for mosfeprojects. Price. $1 These show dimensions 
and positions of holes and cut-outs, but give no wiring details. 

PRINTED WIRING PATTERNS: We can supply negative transparencies, 
actual size. Price: 50c. We do NOT deal in manufactured boards. These 
are available from advertisers 

BACK NUMBERS: As available. On issues up to six months, face value. 
Seven months to 12 months, face value plus 5c. Thirteen months or older, 
face value plus 10c. Postage and packing, 10c per issue extra. Please 
indicate if a PROJECT REPRINT may be substituted if the complete issue 
is not available. ° 


REPLIES BY POST: These are provided to assist readers encountering 
problems in the construction of our projects published within the last two 
years. Note, particularly, that we cannot provide lengthy answers, or 
undertake special research or modifications to basic designs. Charge. 
50c. Inclusion of an additional fee does not entitle correspondents to 
special consideration. 

OTHER QUERIES. Technical queries outside the scope of ‘Replies by 
Post” may be submitted without fee and may be answered in the magazine 
at the discretion of the Editor. Technical queries will not be answered by 
interview or telephone. 

COMMERCIAL EQUIPMENT: ‘Electronics Australia” does not maintain a 
directory of commercial equipment, or circuit files of commercial or ex¬ 
disposals equipment etc. We are therefore not in a position to comment on 
any aspect of such equipment. 

COMPONENTS: ‘‘Electronics Australia” does not deal in electronic 
components. Prices, specifications etc should be sought from appropriate 
advertisers or agents. 

REMITTANCES: These must be negotiable in Australia. Where the exact 
charge may be in doubt, we recommend submitting an open cheque, 
endorsed with a suitable limitation. 

POSTAGE & PACKING: All charges shown include postage and packing, 
unless otherwise specified 

ADDRESS: All requests for data and information should be directed to the 
Assistant Editor, “Electronics Australia ”, Box 2728, GPO Sydney, NSW, 
2001 —(10/71) 


no 


ELECTRONICS Australia, June, 1972 





















IMPEDANCE MATCHING: Can the Impedance 
Matching Stage published in the Jan 1972 issue in the 
“Elementary Electronics” section be used for mat¬ 
ching the impedance of a crystal mike to that of a 
dynamic one? (G.C., Bendigo, Vic). 

^ As it stands, the Impedance Matching stage has an 
input impedance of around 50k, which is too low for a 
crystal microphone. The input impedance could be 
raised by using a high-gain transistor such the BC109 
with an emitter resistance of 10k, and two base bias 
resistors of 4.7M each. This will produce an input 
impedance of approximately 1.5M, assuming a 
following amplifier input impedance of greater than 
20k. 1.5M is still on the low side for a crystal 
microphone but it may. suffice for your purpose. 

CONGRATULATIONS: I am a relative beginner in 
electronics, but have been reading your magazine for 
over a year. I think it is the best. Congratulations on an 
excellent layout, selection of articles and variety of 
projects. I recently constructed the proximity switch 
but have been unable to buy the specified transformer 
in any brand. Could you advise me of suppliers of the 
component. Also, have you ever described a 
fluoroscope with the associated X-ray apparatus. 
(E.R., Joondanna, W.A.) 

v^Thank you for the compliments, E.R. The trans¬ 
former we used in the Proximity Switch was a 
Ferguson type PF2235. As you live in Western 
Australia, the Willis Trading Company (who advertise 
regularly in the magazine) may be able to supply or 
order the transformer. We have not described any 
fluoroscope or X-ray apparatus. These devices would 
be much too dangerous for use by inexperienced 
people. 

DIGITAL EQUIPMENT: I have been a reader of your 
magazine for ten years and would like to compliment 
you on the high quality. However, there is one field of 
electronics you have tended to ignore — that of digital 
electronics. The last project you did along this line was 
the 70MHz Digital Frequency Meter in May 1970 — 
over two years ago. Some US magazines have been 


NOTES AND ERRATA 

LOW NOISE PREAMPLIFIER: (September 1971, File 
No 1 / PRE / 26) Constructors who have coupled low 
impedance cartridges to the input via an impedance 
step-up transformer have found the unit deficient in 
bass response. This unit requires a low source im¬ 
pedance in order that the feedback loop will function 
correctly. To solve the problem remove the 1M resistor 
(R2) and experiment with the values of Rl, C2 and C3. 

PLAYMASTER GUITAR AMPLIFIER VIBRATO: 
Certain models of the Playmaster Guitar Amplifiers 
incorporate an LDR as part of the vibrato system. 
Some readers have experienced a problem of volume 
change as the “Depth” control is varied from one 
extreme to the other. To encompass device spread in 
the LDRs used in this section, replace the 15k resistor 
at the zero end of the Depth control with a series 
combination of a 22k preset potentiometer and 4.7k 
resistor. With the vibrato “off”, adjust the preset pot 
for no change in volume level from one extreme to the 
other of the “Depth” control. 

LOW COST STEREO (Jan 1972): Two 3.3k resistors, 
shown on the circuit diagram have been omitted from 
the parts list. “2 8uF 18VW” should read “1 8uF 
18VW”. The 10k stabilising resistor shown on the 
circuit diagram from the moving arm of the volume 
control is placed in the moving arm of the bass control 
on the circuit board. These positions should be linked 
and the resistors placed on the top of the board in the 
volume control circuit as per the circuit diagram. 

PLAYMASTER 132 AMPLIFIER (June 1971): If 
difficulty is experienced with setting the power supply 
output to 60 volts, an increase of the 6.8k resistor in the 
lower arm of the “Set 60V” preset pot to 12k should 
allow sufficient adjustment range if tolerance ex¬ 
tremes of components is encountered. 

CRYSTAL LOCKED HF RECEIVER (March 1972): A 
330pF disc ceramic capacitor from pin 3 of the TAA840 
IC is shown connected to common foil. It should be 
connected to the emitter of the BF194 local oscillator 
transistor (centre pin) at right angles to the IC axis. In 
some cases, the inclusion of a O.luF ceramic disc 
capacitor from the speaker “hoV’ terminal to the 
common foil area may be required to stabilise the 
audio section against RF problems. Usually, tight 


very active in this area. I would like to build some 
digital projects — possibly a digital multimeter and a 
digital clock. I hope you will consider publishing these 
in the near future. There are no doubt many more 
readers who would be interested. (.R.S., Hawthorn, 
Vic.) 

& No doubt there would be some readers interested in 
digital equipment, R.S., but we have reservations as to 
the number who would build this type of equipment if it 
were described. It is fair enough to say that US (and 
other) magazines feature this very regularly — but 
they are not faced with many of the supply problems 
which we are in Australia. Perhaps the greatest of 
these is the cost. We have inflated prices for imported 
components and, in this particular field, the supply of 
local components is relatively limited. So anything we 
make is bound to cost more than a similar device in the 
US or Europe. Again, there is the problem of appeal. 
An electronic digital clock may look impressive but, 
considering the cost, is it really more functional than, 
say, a “flip-over" type numerical clock which can be 
obtained for less than twenty dollars? TTie same 
comments apply, in many applications, to digital 
multimeters as against conventional VTVM’s. 

PENFRIEND WANTED: I am 14 years old and read 
Electronics Australia every month. I would like a 
penfriend of my age who is also interested in elec¬ 
tronics and SWL. Could you please print my name and 
address. Also, I would like to build a BFO, and hear 
from anyone who has a circuit for a Philips 175A 
receiver. (Wayne Newport, 19 Lookout St, Thirroul, 
NSW 2515) 

®As you can see, we have printed your name as 
requested. Our latest BFO was described in the Sep¬ 
tember 1970 issue (File No. 2 BFO 3). Reprints are 
available through the Information Service. 

ELEMENTARY ELECTRONICS: I have ordered a kit 
for the beginners organ and would like to know if you 
could publish a small, simple amplifier with a three 
inch speaker in the “Elementary Electronics” section. 
I enjoy reading “Electronics Australia” and find the 


twisting of the volume control leads is all that is 
required. To guard against marginal instability, it may 
be necessary in some instances to link pins 6 and 14 of 
the IC with a short piece of wire on the foil side of the 
board. The inclusion of a 250uF / 12V electrolytic 
capacitor may also be required across the supply line 
after the switch to ensure stability towards the end of 
battery life. 

130 RECEIVER: (April 1972, File No 2/SW/62). 
On page 33, the 4-20V lead on the audio board should go 
the hole in the copper adjacent to the collector of TRIO. 
The oscillator coil consists of 40 turns centre tapped, 
with 4 turns over the earthy end. 

TUCKER TIN SSB TRANSMITTER (Feb-April 1972): 
In Fig 13 reproduced on page 61 of the March article, 
the jack shown for connection of the CW key should be 
a closed-circuit type. 

PLAYMASTER 132 AMPLIFIER (June 1971) To 
reduce the risk of failure of the power supply trans¬ 
istors TR27 and TR28 under certain conditions of short 
circuit trip-out, a BY 126-100 (or similar) silicon rec¬ 
tifier diode should be placed between the emitter of 
TR28 and the base of TR29. This can easily be done by 
mounting the diode on a small tagstrip adjacent to 
TR29 (mounted on the back panel), and connecting the 
flying lead from the circuit board to the anode of this 
diode in lieu of the base of TR29. The cathode of the 
diode is then connected to the base of TR29 with a short 
jumper lead. 

AC REGULATOR FOR ENLARGERS (Feb, 1972, File 
No 2 / PC / 17): Although we made extensive enquiries 
before describing this project on the availability of 110 
volt enlarger lamps — and were assured stocks were 
available — it appears that some readers have had 
problems in obtaining them. We have located some of 
these lamps, which are available, via retailers, from 
Sixteen Millimetre (Aust) Pty Ltd, of 55 Murray Street, 
Pyrmont, NSW 2009. Three wattages are available, 
namely 75,150 and 300. The recommended retail prices 
are, respectively, $1.50, $1.80and $3.50 (plus sales tax). 
Victorian retailers should direct enquiries to the 
Melbourne office of Sixteen Millimetre. We strongly 
suggest readers do not start construction of this project 
until the correct bulbs are actually in hand. 



STA 


ELECTRONICS P/L 

Manufacture — Sales — 
Service 

392 Centre Road, Bentleigh, Vic, 
3204. Tel: 97 4832 AH. 97 5539 
NOW AVAILABLE - 
TRANSISTORISED 

ULTRA-VIOLET 


BATTERY PORTABLE LIGHT. 


Can be used for Prospecting, 
Mineral Identification, Fluorescent 
Research, Secret Messages, Plans, 
Party Fun, etc. 



COMPLETE WITH BATTERIES 

NOW AVAILABLE 
IN INEXPENSIVE 
KIT FORM 


METAL DETECTOR/ 
TREASURE FINDER 

Printed board, 5 transistors, all 
electronic components. With battery. 
Special Introductory Price 

$19.00 

COMPONENT BARGAINS 


Mono 3 speaker selector $2.70 

Stereo 3 speaker switch $4.20 

X-over with tweeter pot $2.70 

Headphone adaptors $2.75 

Foot switches $2.85 


PANEL METERS 


8 ^ 812-8 

OP3006-C 

OP450S-C 

OP7196-C 

OP7376-C 

OP8OOO-C 

OP8020-C 

OP8030-C 

OP8050-C 

OP8O6O-C 

OP7073-C 

OP8070-C 



360ft. 10 mil plastic fibre 6ft lenatns 

« ft. 20mll plastic fibre 6ft lengths . 

ft. 30mll plastic fibre 6ft lengths . 

36ft. 45mil plastic fibre 6ft lenoths . 

6ft. jacketed fibre 19 x 17mil fibres 
6ft. lacketed fibre 37 x 17mil fibres 
4 channel light head 6-12v AC/DC 

2 bulbs 3 watts (low heat). 

Eyelet assortment for fibre endings . 

Adhesive end-treat compound. 

Fibre Optic Manual. 

3ft. jacketed fibre 7 x 17mil fibres 
This is a special introductory 
Fibre Optic Kit offer normal value 
$14.52 Super Special at only .$10.63 



ELECTRONICS Australia, June, 1972 


111 





















TTL GATES Dual in Line 

7400 quad 2 input nand .30 

7401 quad 2 input nand .30 

7402 quad 2 input nor .30 

7404 hex inverter .30 

7405 hex inverter .30 

7410 triple 3 input nand .30 

7420 dual 4 input nand .30 

7430 8 input nand .30 

7440 dual 4 input buffer .30 

7450 expandable dual 2/2 and/or .30 

7451 dual 2/2 and-or .30 

7453 4/ 2 and-or .30 

7460 dual 4-input expander .30 

74H00 .40 

74H01 .40 

74H04 * .40 

74H10 .40 

74H20 .40 

74H51 .40 

74H61 .40 

8424 low power dual RS/T .30 

8H2175 MC (typ.) dual JK 1.25 

LU321 dual JK "Utilogic" -60 

7472 JK 2/ and inputs .40 

7473 dual JK .65 

7474 dual type "D" .50 

7476 dual JK 2/set and reset .65 

74107 dual JK .60 

7490 decade counter l .40 

7492 divide by 12 counter 1.40 

7493 4 bit binary counter 1 .40 

8280 45 MC presentable decade counter 1.40 

8281 45 MC presentable binary counter l .40 

74192 up/ down decade counter 2.25 

8520 25 MC divide by "N" 2 to 15 2.00 

74193 up/ down binary counter 2.00 

7406 hex inverter buffers / drivers with 

30v open collector 2.00 

7408 quadruple 2-input positive and gates .40 

7411 triple3-input and gate .45 

7413 dual 4-input nand Schmitt triggers 1.75 

7489 64 bit random access memories 4.00 

74123 dual retriggerable monostable 
multivibrators with clear 2.50 

7475 quad latch 1.50 

7480 gated full adder .80 

7483 4 bit full adder 1.60 

74121 one shot multivibrator 1.25 

74122 one shot multivibrator 1.50 

7491 8 bit, SI, SO 1.40 

7495 4 bit PI, PO, LR 1.40 

74195 4 bit PI, PO 1.40 

8570 8 bit SI, PO 3.00 

8590 8 bit PI, SO 2.00 

8270 4 bit PI, SI, PO, SO 1.40 

7441 BCD "Nixie" decoder 1.50 

7442 BCD decoder driver 1.40 

7446 7 segment 30v driver 3.00 

7447 7 segment I5v driver 2.50 

7448 7 segment decoder 1.40 

74154 1 of 16decoder (24 pin) 2.50 

74153 dual 4 to 1 line selector 4 bit 

magnitude comparator A,>B, A,>B, A>B 
outputs 1.60 

8210 8 line to 1 line selector 1.40 

8220 parity gen/checker .75 

7486 exclusive (quad) or .65 


DTL GATES 


MC830 dual 4 In expandable nand 

.35 

MC836 hex inverter 

.35 

MC846 quad 2 input gate 

.35 

MC862 triple 3 input gate nand 

.35 

MC852 dual JK DTL 

.70 

MC853dual JK DTL 

.35 


LINEARS — PACKAGE AS NOTED 

LM100 positive dc regulator TO-5 device provides 20 
ma, 2-35v out (up to 5 amps, with ext. transistors.) 
TO-5 .80 

NE526 high speed comparator 1.00 

N E565 phase lock loop TO-5 5.75 

NE566 function generator TO-5 or DIP (8 pin) no 

choice 5.75 

NE567 tone decoder DIP (8 pin) 5.75 

709 popular op amplifier DIP .50 

710 voltage comparator DIP .65 

711 dual comparator DIP .75 

741 compensated op-amp TO 5 .75 

5558 dual 741 op-amp (8 pin) DIP 1.25 

LM302 op-amp voltage follower 1000 megohm input 

.999v gain TO-5 1.25 

747Dual 741 op-amp DIP 1.25 

LINEAR SPECIAL 

Ten (10) 741 fully compensated operational am¬ 

plifiers with data sheer and two (2) pages of ap¬ 
plication notes covering the basic circuits for op- 
amps. 

EACH .70 PACKAGE $6.50 

Please specify first and second choice of: TO-5, 8 pin 
MINI DIP, 14 pin DIP. 

LM309K — 5 volt regulator — 
This TO-3 device is a complete 
regulator on a chip. The 309 is 
virtually blowout proof, it is 
designed to shut itself off with 
overload of current drain or 
over temperature operation. 
Input voltage (DC) can range 
from 10 to 30 volts and the output 
will be five volts (tolerance is worst case TTL 
requirement) at current of up to one ampere 

Each $2.40 
Five for $10.00 



COUNTER DISPLAY KIT — CD — 2 

This kit provides a highly 
sophisticated display section 
module for clocks, counter or 
other numerical display needs. 
The RCA DR-2010 Numitron 
display tube supplied with this 
kit is an incandescent seven 
segment display tube. The 6 inch 
higher number can be read at a 
distance of thirty feet. RCA 
specs, provide a minimum life 
for this tube of 100,000 hours 
(about 11 years of normal use). 
A 7490 decade counter 1C is used 
to give typical count rates of up 
to thirty MHz. A 7475 is used to 
store the BCD information 
during the counting period to 
ensure a non-blinking display. 
Stored BCD data from the 7475 is 
decoded using a 7447 seven 
segment decoder driver. The 
7447 accomplishes blanking of 
leading edge zeroes, and has a 
lamp test input which causes all 
seven segments of the display 
tube to light. 

Kit includes a two sided (with plated through holes) 
fibreglass printed circuit board, three IC's, DR-2010 
(with decimal point) display tube, and enough Molex 

socket pins for the IC's. 

Circuit board is 8 inches wide and 4 3 /s inches long. A 
single 5 volt power source powers both the IC's and 

the display tube . 

CD-2 kit complete only $12.00 assembled and tested 
$13.00 



RCA DR2010 Numitron 
digital display tube. 

This incandescent five 
volt seven segment 
device provides a 6 inch 
high numeral which can 
be seen at a distance of 30 feet. The tube has a 
standard nine pin base (solderable) and a left hand 
decimal point. 

Each $5.00 




LED DISPLAY 

Seven segment diffused planar GaAsP light emitting 
diode array. It is mounted on a dual in line 14 pin 
substrate and then encapsulated in clear epoxy for 
protection. It is capable of displaying all digits and 
nine distinct letters. 

Features: 

High brightness . . typically 350 ft-L at 20ma. 

Single plane, wide angle viewing.150 degrees. 

Unobstructed emitting surface 
Standard 14 pin dual in line package 
Long operating life . . . Solid state 
Operates with 1C voltage requirements. 

Only $4.50 


ME-2 Invisible infrared emitter 
high power, 1A at 1.5V TO 5 $3.00 



Light Emitting Diode Devices (LED) 

MV-50 visible red emitting 10-40ma at 2V .60 
10 for $5.00 



MV-10B Visible red emitter 
5-70maat2V .75 


BUY STATE OF THE ART SEMI CONDUCTOR PARTS DIRECT FROM THE USA 

All goods are sold on a money back giarantee. 

All prices are in Australian currency, we will accept money orders, bank cheques, and 

company cheques (from rated firms) in Australian dollars. 

Goods are shipped within 24 hours of receipt of order. 

Goods will be carefully packed and all custom forms will be attached .... 

Due to paper work and high postage costs we cannot accept orders for less than $5.00. 
Orders for more than $ 10 will be shipped via Air Mail, orders for less will be shipped surface 
mail ... 

Do not add anything for postage, it is included in price. 


BABYLON 

ELECTRONICS 

P. O. BOX J 

CARMICHAEL, CALIFORNIA 95608 

(916) 966-2111 


112 


ELECTRONICS Australia, June, 1972 






































PA AMPLIFIER . . (from Page 49) 

coupling capacitor should be within 1 volt of 
half the supply voltage, ie, if the supply 
voltage is 48 volts, the voltage across the 
capacitor should be between 23 and 25 volts. 

Having connected the power amplifier 
and assured that it is working correctly, 
the mixer board can be connected. The 
voltages on this board should be measured 
with a 20,000 ohm / volt meter and should be 
within 1 volt of the values indicated on the 
circuit. 

Incidentally the amplifier may be 
operated safely without a load. 

The following is a list of precautions 
which should be followed to ensure reliable 
operation : 

(a) The main amplifier must be built on 
the printed board. Other methods of con¬ 
struction may lead to instability and 
“motorboating”. 

(b) Never connect the power amplifier IC 
to the supply unless it is properly bolted to 
the rear of the chassis or an efficient 
heatsink. 

(c) Do not short the output intentionally. 
In the event of accidents the fuse should 
blow, but it is an unwise practice to “tempt 
fate”. 

Careful attention to the details of this 
article should provide a high performance 
unit that should give years of reliable 
service. & 

w 


SERVICEMAN . . . (from Page 55) 
to its full height. 

That was enough. I reefed the capacitor 
out and measured it. It was a better resistor 
than a capacitor, tipping the scale at a neat 
1 megohm. 

Which was all very gratifying, but I was 
still puzzled as to the purpose of the 
capacitor, particularly as its removal had 
no apparent effect on the behaviour of the 
set. 

Finally, I rang the manufacturers. Their 
explanation was that it was originally in¬ 
cluded “. . . to counter problems due to 
flashover in the tube.” 

I must confess I was somewhat puzzled by 
this statement. For one thing I was sur¬ 
prised that such a precaution should be 
necessary in a valve set, and also that the 
precaution should take this form. 

While I have seen plenty of sets fitted with 
protective devices between the picture tube 
pins, these have invariably been transistor 
sets, the risk being that flashover inside the 
tube could damage expensive transistors. 
And the protective devices have invariably 
been spark gaps, not capacitors. 

I can only assume that a surge or spike of 
some kind was anticipated on one or other of 
these lines and the capacitor was intended 
to take some of the sting out of it. 

As it transpired, these speculations were 
somewhat academic, because the chap at 
the other end of the phone went on to explain 
that the capacitor had given a lot of trouble 
due to leakage, and it was now recom¬ 
mended that it be deleted. Presumably it 
created more trouble by going leaky than it 
prevented by controlling the anticipated 
spikes. 

Nor would this be the first time something 
like this has happened in the TV industry. 


ANSWERS . . . (from Page 111 ) 


“Elementary Electronics” section most useful. The 
other sections seem to be a little too advanced for me. 
Perhaps you could publish a project which you think 
would be suitable for a school club — one which is 
reasonably cheap. (J.S., Wudinna, SA.) 

®Thank you for your suggestions and the remarks 
about the “Elementary Electronics” section. We are 
pleased to learn that it is helping some of our younger 
readers. We have been thinking of projects along the 
lines which you have suggested for some time, and will 
try to schedule them in the not too distant future. 

COLOUR TV: With the advent of colour TV to 
Australia shortly, I would like to know if there is any 
information available on the theory of operation of the 
camera equipment. I can understand the operation of a 
black and white camera, but cannot find any in¬ 
formation on colour cameras. (J.G., Quakers Hill 
NSW). 

®Information on colour camera theory and operation 
can be obtained from such publications as RCA 
Review, Philips Technical Review, and Milliard 
Technical Communications. A browse through a 
library at a tech college or university will probably 
yield the above publications, together with other books 
on the subject. 

MUSICOLOUR: I am in the process of building a 
Musicolour 2, as in the December 1971 issue. I am 
having difficulty in obtaining the FETs and PUTs. I 
have some 40583 Diacs which I am thinking of using 
instead of the PUTs. Will they work? Could you tell me 
the prices of the board 71/cl2, and the metalwork. 
(M.V., Christchurch, NZ.) 

&The Diacs cannot be used in the Musicolour 2, MV. 
They would certainly not work. The Musicolour 1 
(October 1969, File No 2 / PC / 8) used diacs, but, it is 
nowhere near as sensitive as the Musicolour 2. 
“Electronics Australia” does not deal in parts, etc, for 
the projects it features. Enquiries for these should be 
direct to the advertisers concerned. 

DIODE RATINGS AND HUM ELIMINATION: Please 
accept my compliments on a fine magazine. I must 
agree with T.L. of Arncliffe re the dating of the spine 
for the volume binder. Referring to diode ratings, what 
is meant by PIV? Also, is there any way of eliminating 
hum developed between a record player and am¬ 
plifier? (G.C., Ouyen, Vic.) 

®Thank you for your comments about the magazine 
and binder, G.C. The term “PIV” as applied to data on 
diode ratings, refers to the “peak inverse voltage”, or 
the absolute maximum allowable voltage that can be 
applied across a diode in the reverse biased mode. It is 
particularly important where the rectifier is feeding a 
capacitor, as in a typical power supply filter network. 


During the half cycle when the rectifier is not con¬ 
ducting, the voltage applied to it in the reverse 
direction will be the sum of the voltage across the 
capacitor and the voltage across the AC supply ter¬ 
minals, these two voltage sources being effectively in 
series. As an example, the minimum peak inverse 
voltage rating a diode must have when feeding a 
capacitor input filter, is 1.4 times the RMS AC voltage, 
PLUS the DC across the capacitor, which is also 1.4 
times the RMS input. In other words, 2.8 times the RMS 
input to the diode rectifier. In the case of a bridge, each 
diode sees 1.4 times the RMS input. Mains hum 
produced when a record player is connected to an 
amplifier is usually caused by “earthing” 
arrangements between the amplifier and pickup, and 
record player and power outlet. Generally the easiest 
way to eliminate the hum is to isolate the pickup arm 
and its shielded cable from the record player deck, and 
connect to the amplifier by the shielded cable only. The 
record player return can then be run either to the 
power point, or to the amplifier chassis. Hum can also 
be introduced by magnetic radiation from the player 
motor, but this can only be minimised by choice of a 
suitable mounting position for the pickup arm. ^ 


POSITION VACANT 

(part time) 

Preferably student, servicing ultra¬ 
miniature audio equipment. 

Phone Melbourne 63 4781 


SERVICE 

BILL TURNBULL offers you 
service on Hi Fidelity equipment 
tape Recorders, Communication 
Receivers and Electronic Test 
Equipment. 

All work guaranteed 

BILL TURNBULL 

11 ELLALONG ROAD, 
CREMORNE. N.S.W. 90 4825 


HAM 


RADIO 

SUPPLIERS 

MAIL ORDER SPECIALISTS 


323 Elizabeth St. (2 doors from Little Lonsdale St.) 

Melbourne, Vic. 3000. Phones: 67 7329, 67 4286. 

MODEL C-1000 POCKET MULTIMETER, 1000 ohms/ oer Volt, AC Volts; 0-10/ 50/ 250/ 1000 (1000 opv). DC 
Volts: 0-10/ 50/ 250/ 1000(opv), DC Current: O-lOOmA Resistance: 0-150K ohms (3K centre). 2 colour scale. 
Range Selector Switch. Dimens.: 3V? x 2'/4 x 1 in. $6.75 Post Free. 

MODEL OL-64D MULTIMETER, 20,000/ OPV, DC Volts: 0-0.25/ 1/ 10/ 50/ 250/ 500/ 1000V at 20K/ OPV 
5000 volts at 10K/ OPV, AC Volts: 0-10/ 50/ 250/ 1000V at 8K/ OPV, DC/ A: 50uA/ 1mA/ 50mA/ 500mA/ 10 
amps. RESISTANCE: 0-4K/ 400K/ 4M/ 40Megohm, DB Scale:—20 to plus 36db. Capacitance: 250pF to .02uF, 
Induct, 0-5000H, size 5 3 A x 41 / 8 x PAin. $19.75 P.P. 40c 

NEW MODEL US-100. Overload protection. Shockproof Movement, polity switch, DC volts- 
P 2 ^, 1 /- 25 / 10/ 50/ 2507 1000V (20K / OPV) AC Volts: 10 25, 10/ 50/ 250/ 1000V (5K/OPV). DC/ Amps: 
1mA/25mA/ 500mA/ and 10A. AC/Amps 10A. RESISTANCE: 0-50M/ohms (centre scale 50) R X 
1/ 10/ 1000/ IK/ 10K,db scale—20 to plus 10 plus22/ plus35/ plus50db. $29.90 P.P. 40c. 

US106 as above but 50,000/ o.p.v. $34.00 P.P. 40c. 

MODEL AS100 DP HIGH SENSITIVITY 

100,000/Ohms/volt DC, Mirror Scale, PROTECTED MOVEMENT, SPECIFICATIONS: 
6/ 20/ 120/ 300/ 600/ 1200 Volts A.C., (10K/ OPV), Volts D.C.: 3/ 12/ 60/ 120/ 300 7 600/ 1200 (100K OPV) 
D.C. Amps: 12uA/ 6mA/ 60mA/ 300mA/ 12 Amps. RESISTANCE: 2K/ 200K/ 20Mg/ 200Meg, Decibels:—20 
to plus 63dB. AUDIO OUTPUT: 6 Volts/ 30/ 120/ 300/ 600/ 1200V A.C., SIZE: 7V 2 in. x 5V 2 in. x 2% in. $34.50 
P.P. 40c. 

1 12 TRANSISTOR, 3 CHANNEL and call System. Specifications: Cir¬ 

cuit: 13 Transistors, 1 Diode, 1 Thermistor. Range: Up to 10 miles (depending on terrain, etc.). 
Frequency: 27.240 MHz (PMG approved) Freq. Stability: Plus or minus 0.005°}. Transmitter: 
Crystal controlled, 1 watt. Receiver: Superheterodyne, Crystal controlled. Antenna: 13 Section 

^^^ rCe: 8 1,5 v ° lf pen batts - Size 8'/4in. x 3V4in. x l^in. Weight: 25 ozs. 

Other features. Leather carrying case, battery level meter, squelch control, earphone jack, A C. 
adaptor lack, etc. Price —$79.50 pair. Be early! 

“TRIO" 9R59DS. (General coverage.) 4 bands covering 540 kcs, valve type, to 30 mcs.'Two mechanical filters 
ensure maximum selectivity. Product detector for SSB reception. Large tuning and bandspread dials for 
accurate tuning. Automatic noise limiter. Calibrated electrical bandspread. "S" meter and B F O 2 
microvolts sensitivity for 10 db S/ N ratio. Price $178.50. 


ELECTRONICS Australia, June, 1972 113 





















Do not start to build yourself an 
organ without first finding out about 
the superb SCHOBER (USA) 
assemble-it-yourself kits. Inquiries to 
Schober Organs (Aust), 124 Living¬ 
stone Ave., Pymble, NSW, 2073. 
(Mail only please.) 


THE RECIPROCATING 
DETECTOR 

— A remarkable development in 
communications technology. Read 
about it in the June Australian EEB. 
Also, "Modulated Light Com¬ 
munication", and much more. 

— EEB is always late, so you still have 
time to get your June issue. Send 
$1.55 for a year's worth of EEB (6 
issues) to: 

THE SUBSCRIPTION 
MANAGER, EEB 
115 Wilmot St, Huonville, 
Tasmania. 7109. 


— C.D.I. TRANSFORMERS- 

6 & 12 volt negative and positive polarities. ONLY 
$6.00 incl tax. Pack and post 50c extra. Free 
converter circuit supplied with every trans¬ 
former. 

See page 115 Jan 71 'Electronics Aust' 

F. MIHAI 
48 CHAPEL ROAD. 
MOORABBIIM VIC 3189 Tel 95 4839 


"Amateur Electro-plater's Guide." 

Elementary practical text describes fully how 
to plate at home with copper, nickel, silver, 
gold, rhodium, also aluminium anodising. $1.30, 
including postage. Available only from: 

Patrician Trade Services, 

P.O. Box 114, Stafford, a 4053 


MODERN ELECTRONICS 

Due to successful advertisement in the past, we 
are pleased to offer the following specials. ... All 
marked and guar... 

Popular 200H multimeter $9.95 complete V 2 watt 
S c /c resistors 1 ohm to 10 meg 3.5c each, $2.75 per 
100; 1 watt 6c or $5 per 100; 0a91 diodes 20c $1.80 
per 10; EM401 25c $2.20 per 10; EM404 30c $2.80 per 
10;BC107, 8 or 9 35c each or $3 per 10; Speaker cable 
2c foot $5.50 100yds hookup cable in 10 colours 4c 
yd; all gauges winding wire available. Magnetic 
earpieces 3.5mm plug 35c $3 per 10. Alligator clips 
(4 colours 10c, $1 per 12; UG88u coax connectors 
$1.35 each. Tantlum capacitors all in ufd. .1, .47, 
1, 2.2, 3.3 (35v) 4.7, 6.8 (25v) 10 (16v) 15 (lOv) 22 
(6.3v) at 25c each, any 10 at less 10* <. lOuf (25v) 22 
(16v) and 50 (6.3v) at 35c each. BAX13 diodes at 
35c each. BRY39-3N81 and BD182 on application. 
All prices include tax. Plus postage. We stock a 
complete transistor range. 

Many others, come visit our showrooms for fan- 
tastic specials. Write today for free semi¬ 
conductor price list. All inquiries welcome, in¬ 
cluding Pacific Islanders and Asians. $NZ, Fiji and 
US accepted. 

Open Friday nights. Other nights can be arranged. 
Ring 654 3761. Modern Electronics 94 Elizabeth 
Street, Melbourne. All mail to GPO Box 5402CC, 
Melbourne, Victoria 3001, Australia. 


POWER 

MODULES 



• Single and Dual Outputs 

• Output Voltages to 50 Volts 

• Output Current to 2.0 Amps 

• Line and Load Regulation — Less 
than 0.01 7. 

• Short Circuit proof 


SCIENTIFIC ELECTRONICS 
PTY LIMITED 

42 Barry Street. Bayswater, 
Vic 3153. Phone: 

Melbourne 729 3170; Brisbane 
474311; Adelaide 771325; Perth 
21 6146 


COLLINS 

COMMUNICATIONS 

RECEIVERS 

Inquiries are invited for the purchase of as 
new Collins Communications Receivers type 
390 & 390A^.5 to 32MHz. Digital Read Out. 
1MHz Bands. Dial Calibration 200Hz. Crystal 
synthesising driftless Rx.” (Finance 
Available). 

Apply in writing to: 

Industrial and Medical Electronic 
Company, 

6th Floor, 288 Little Collins Street, 
MELBOURNE. 

Phone: 63-9258. 


WHY TRAVEL TO THE CITY??? 
ELECTRONICS SPARES 


102 Qu*«n St.. ST. MARYS. N.S.W. 2760 
SEMICONDUCTORS 


AC125 

.74 

MPF102 

.78 

2N54593 

11.00 

AC127/ 128 $1.70 

0C44N 

.48 

2N54853 

11.50 

AC 187/ 188 SI.90 

0C45N 

.48 

AY61083 

11.36 

AD149 

*2.10 

OC72 

.48 

AY61093 

11.36 

AD161/162 S2.95 

OC74N 

.75 

AA119 

.30 

AF116N 

.75 

OC75N 

.75 

BA 100 

.36 

BC107 

.55 

0C81 

.65 

BA102 

.96 

BC108 

.40 

TT797 5 

12.00 

BA114 

.31 

BC109 

.45 

TT798 3 

12.20 

0A5 

.55 

BC177 

.75 

TT800 3 

11.36 

OA90 

.26 

BC178 

.70 

TT801 3 

11.36 

0A91 

.17 

BC179 

.75 

2N26463 

11.30 

OA95 

.31 

BD139/ 140 S5.20 

2N2926 

.75 

OA202 

.46 

BF115 

.63 

2N30543 

11.95 

IN914 

.31 

BF167 1 

ti.oo 

2N30553 

12.00 

A15A 

.75 

BFY50 ! 

51.10 

2N3638 

.55 

EM401 

.25 

D13T1 : 

11.35 

2N 4360 SI. 20 

FM404 

.30 

Pack & Post .. 

.. 20c Phone 623-0346 for C.O.D. 



A CURE FOR 
ELECTRICAL ILLS 




2-26 


ELIMINAfES MOISTURE 
PROBLEMS-DEPOSITS 
THIN FILM MOISTURE 
BARRIER-PREVENTS 
CORROSION OF METAL 
-LUBRICATES, PENE 
TRATES, CLEANS. 


PREVENTS 80% OF 
ALL ELECTRICAL -- 
FAILURES! 


... the 

"TOOL KIT 
IN-A-CAN" 

with The 

QUICK 

FIX-IT 

mm 

us 


USE IN INDUSTRY. 

ON — Air Conditioners, Alarms, Battery Cables, Blowers, 
Bulb Terminals, Bus Bars, Bushings, Cable Lubricant, Cir¬ 
cuit Breakers, Coils, Coin Slots, Conductors, Conduits, 
Contacts, Controls, Elevator Equip., Fans, Filters, Fire 
Alarms, Fixtures, Fuses, Gauges, Generators, Hearing Aids, 
Housings, Ignitions, Instruments, Meters, Microphones, 
Motors, Oscillators, Panel Boards, Parking Meters, Plugs, 
Potentiometers, Receivers, Receptacles, Refrigeration, Re¬ 
lays, Rheostats, Signal Systems, Sockets, Solenoids, Speak¬ 
ers, Switches, Switch Gear, Synchronisers, Telephone 
Equip., Terminal Blocks, Timers, Tooling, Transformers, 
Transmitters, Tubes, Welders, Wet Splices, Wire & Cable. 


available from your Electrical Wholesale Distributor. 
A HIGH QUALITY PRODUCT OF 


CRC CHEMICALS AUSTRALIA PTY. LTD. 



114 ELECTRONICS Australia, June, 1972 







































BASF’s new 
Chromdioxid 

cassette brings you 
the other hair 
of the fiddle 




Distributors: Sydney: Maurice Chapman & Co. Pty. Ltd., 276 Castlereagh St., 2000. Newcastle- W I 
Redman Agencies, 11 Hall St., N.S.W., 2300. Fyshwick: Sonny Cohen & Sons, 20 Isa St., A.C.T 2600 
Hawthorn: Maurice Chapman & Co. Pty. Ltd., 146-150 Burwood Rd., Vic.. 3122. West End: Chandlers 
Pty Ltd., 399 Montague St., Old., 4101. Unley: Neil Muller Pty. Ltd., 8 Arthur St., SA 5061 Belmont- 
Anderson-Tedco 11-13B Belmont Ave„ W.A., 6104. Launceston: P. & M. Distributors, 87A Brisbane 
St., Tas., 7250. Darwin: Pfitzners Music House, 2 Darwin Arcade, Smith St., N.T., 5790. 


FIRST IN TAPE 


Only 

BASF's new 
Chromium 
Dioxide coating 
can give you a 
dynamic range 
good enough to 
reproduce the 
most subtle tops 
of a violin. Or the 
deepest notes of 
a double bass. 

Until now cas¬ 
settes have had 
poor bass 
response- 
and even 
poorer 
treble res¬ 
ponse. They 
only gave you 
half the sound. 
BASF’s new Chrom¬ 
dioxid lets you hear 
it all. 

And BASF’s new 
internal transport 
system prevents 
foul-ups, no matter 
what tape thickness 
you use. It also stops 
the wow and flutter you 
get from variations in 
tape tension. Chromdi¬ 
oxid cassettes give you 
sound quality that you 
would only expect 
from reel to reel. 
Without all the 
fiddling. 


c 


BA1969 



















40,000 Technicians 

can't be 
wrong! 


• More than 40,000 ambitious men 
have benefited from A.R.T.C. 
training. 

• Join this large number of success¬ 
ful men! 


• Attain job security and financial 
reward. 


• These can only be yours from: 


• ESTABLISHED OVER 40 YEARS 

• OVER 15 FULL TIME STAFF TO ASSIST YOU 

• FULL NIGHT-CLASS PRACTICAL LESSONS 

OR 

• EXTENSIVE CORRESPONDENCE TRAINING WITH SPECIAL PRAC¬ 
TICAL HOME-TRAINING KITS 


Mail Coupon 

NOW # You are invited to mail the coupon below which can be your first step towards securing 

a job or business of your own with good prospects, security and big money. A.R.T.C. will mail to you by 
return, at no obligation to you the big free booklet: “Careers in Radio and Television". This booklet will 
show you definite steps you can take for a better job, how you can succeed in life. Post the coupon, phone 
or call NOW. 


AUSTRALIAN RADIO 
AND TELEVISION 
COLLEGE 

PTY. LTD. 

E.S.ftA. BANK BUILDING. 

Cnr. Broadway and City Road, Sydney. 
(Opp. Grace Bros). Phone 211-4244 (3 line*) 



AUSTRALIAN RADIO & TELEVISION 
COLLEGE PTY. LTD. 

206 Broadway, Sydney, N.S.W. 

Dear Sir, 

Please send me, without obligation, your free book¬ 
let, "Careers in Radio, TV and Electronics”. 

NAME.............. 


ADDRESS 


..E206 4
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